Organic electroluminescent element material, organic electroluminescent element, display device and lighting device

ABSTRACT

An organic electroluminescent element material represented by Formula (1), 
     Formula (1): 
     
       
         
         
             
             
         
       
     
     wherein Z is a heterocylcic ring comprising a substituent having a steric parameter value (Es) of −0.5 or less at the third atom of the ring counted from a nitrogen atom attached to Z, the nitrogen atom being counted as the first atom; and other symbols in Formula (1) are described in the specification.

This application is based on Japanese Patent Application No. 2006-042061filed on Feb. 20, 2006 in Japan Patent Office, the entire content ofwhich is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an organic electroluminescent elementmaterial, an organic electroluminescent element, a display device and anillumination device.

BACKGROUND

Conventionally, an emission type electronic display device includes anelectroluminescence display (hereinafter, referred to as an ELD). Aconstituent element of ELD includes such as an inorganicelectroluminescent element and an organic electroluminescent element(hereinafter, referred to as an organic EL element). An inorganicelectroluminescent element has been utilized as a flat light source,however, requires a high voltage of alternating current to operate anemission element. An organic electroluminescent element is an elementprovided with a constitution comprising an emission layer containing aemitting substance being sandwiched with a cathode and an anode, and anexciton is generated by an electron and a positive hole being injectedinto the emission layer to be recombined, resulting emission utilizinglight release (fluorescence•phosphorescence) at the time of deactivationof said exciton; the emission is possible at a voltage of approximatelya few to a few tens volts, and an organic electroluminescent element isattracting attention with respect to such as superior viewing angle andhigh visual recognition due to a self-emission type as well as spacesaving and portability due to a completely solid element of a thin layertype.

However, in an organic electroluminescence in view of the futurepractical application, desired has been development of an organic ELelement which efficiently emits at a high luminance with a low electricconsumption.

In Japanese Patent No. 3093796, a slight amount of a fluorescentsubstance has been doped in a stilbene derivative, distyrylarylenederivative or a tristyrylarylene derivative, to achieve improvedemission luminance and a prolonged life of an element.

Further, there are known such as an element having an organic emissionlayer comprising a 8-hydroxyquinoline aluminum complex as a hostcompound which is doped with a slight amount of a fluorescent substance(for example, JP-A 63-264692 (hereinafter, JP-A refers to JapanesePatent Publication Open to Public Inspection No.)) and an element havingan organic emission layer comprising a 8-hydroxyquinoline aluminumcomplex as a host compound which is doped with quinacridone type dye(for example, JP-A 3-255190).

In the case of utilizing emission from an excited singlet as describedabove, since a generation ratio of a singlet exciton to a tripletexciton is 1/3, that is, a generation probability of an emitting excitonspecies is 25% and a light taking out efficiency is approximately 20%,the limit of a quantum efficiency (ηext) of taking out is said to be 5%.

However, since an organic EL element which utilizes phosphorescence froman excited triplet has been reported from Princeton University (M. A.Baldo et al., Nature vol. 395, pp. 151-154 (1998)), researches onmaterials exhibiting phosphorescence at room temperature have come to beactive.

For example, it is also disclosed in A. Baldo et al., Nature, vol. 403,No. 17, pp. 750-753 (2000), and U.S. Pat. No. 6,097,147.

Since the upper limit of internal quantum efficiency becomes 100% byutilization of an excited triplet, which is principally 4 times of thecase of an excited singlet, it may be possible to achieve almost thesame ability as a cooled cathode ray tube to attract attention also foran illumination application.

For example, in such as S. Lamansky et al., J. Am. Chem. Soc., vol. 123,p. 4304 (2001), many compounds mainly belonging to heavy metal complexessuch as iridium complexes have been synthesized and studied.

Further, in aforesaid, A. Baldo et al., Nature, vol. 403, No. 17, pp.750-753 (2000), utilization of tris(2-phenylpyridine)iridium as a dopanthas been studied.

In addition to these, M. E. Tompson et al., at The 10th InternationalWorkshops on Inorganic and Organic Electroluminescence (EL'00,Hamamatsu), have studied to utilize L₂Ir(acac) such as (ppy)₂Ir(acac) asa dopant, Moon-Jae Youn. Og., Tetsuo Tsutsui et al., also at The 10thInternational Workshops on Inorganic and Organic Electroluminescence(EL'00, Hamamatsu), have studied utilization of such astris(2-(p-tolyl)pyridine)iridium (Ir(ptpy)₃) andtris(benzo[h]quinoline)iridium (Ir(bzq)₃) (herein, these metal complexesare generally referred to as orthometalated iridium complexes.).

Further, in also the aforesaid, S. Lamansky et al., J. Am. Chem. Soc.,vol. 123, p. 4304 (2001), studies have been carried out to prepare anelement utilizing various types of iridium complexes.

Further, to obtain high emission efficiency, Ikai et al., at The 10thInternational Workshops on Inorganic and Organic Electroluminescence(EL'00, Hamamatsu) utilized a hole transporting compound as a host of aphosphorescent compound. Further, M. E. Tompson et al. utilized varioustypes of electron transporting materials as a host of a phosphorescentcompound doped with a new iridium complex.

An orthometalated complex provided with platinum instead of iridium as acenter metal is also attracting attention. With respect to these typesof complexes, many examples having a characteristic ligand are known(for example, refer to Patent Documents 1-5 and Non-Patent Document 1.).

In any case, emission luminance and emission efficiency aresignificantly improved compared to conventional elements because theemitting light arises from phosphorescence, however, there has been aproblem of a poor emission life of the element compared to conventionalelements. It is hard to achieve an emission of a short wavelength and animprovement of an emission life of the element for a phosphorescentemission material provided with a high efficiency. At present state, itcannot be achieved a level of a practical use.

With respect to shortening of emission wavelength, heretofore, therehave been known introduction of an electron attracting group such as afluorine atom, a trifluoromethyl group, or a cyano group as asubstituent group into phenylpyridine, and introduction of a ligand ofsuch as picolinic acid or of a pyrazabole type. However, when anemission wavelength is shortened to achieve blue color by utilizingthese substitution effects, a high efficiency may be achieved whileemission life will be greatly deteriorated, which requires furtherimprovement to overcome the trade-off relationship.

As a ligand, known are metal complexes having phenylpyrazole in whichthe phenyl group undergoes substitution (refer, for example, to PatentDocuments 1 and 2). In the substitution mode of the phenyl group ofphenylpyrazole, which is disclosed in the above, the lifetime of theluminescent element is improved but is still insufficient. Further, inview of luminescent efficiency, much room for improvement still remains.On the other hand, it has been known that ligands having a substituentexhibiting steric hindrance are appropriate for improvement ofluminance, and there are examples of application to the phenylpyrazolemother nucleus (refer, for example, to Patent Document 3).

Examples of metal complexes, in which phenylimidazole as a ligand isemployed as a basic skeleton, are disclosed (refer, for example, toPatent Documents 4,5, and 7). In the above patent documents, describedis luminescent wavelength, driving characteristics of the elements,external quantum efficiency, and chromaticity, but not specificallydescribed is the lifetime of the luminescent elements.

Further disclosed are examples of luminescent elements incorporatingmetal complexes in which phenylimidazole, phenyltriazole, orphenyltetrazole is employed as a basic skeleton (refer to PatentDocument 6). In above patent document, the driving characteristics ofelements, external quantum efficiency, and chromaticity are described,but the lifetime of luminescent elements is not specifically described.

[Patent Document 1] WO 04/085450

[Patent Document 2] JP-A 2005-53912

[Patent Document 3] JP-A 2003-109758

[Patent Document 4] WO 05/007767

[Patent Document 5] JP-A 2005-68110

[Patent Document 6] US-A 2006-0008670

[Patent Document 7] WO 06/009024

SUMMARY

This invention has been made in view of these problems, and an object ofthis invention is to provide an organic EL element material with acontrolled emission wavelength which have high emission efficiency andlong emission life, an illumination device and a display device byutilizing said element material.

The object of this invention described above has been achieved by thefollowing constitutions.

-   (1) An organic electroluminescent element material represented by    Formula (1),

wherein Z is a heterocyclic ring comprising a substituent having asteric parameter value (Es) of −0.5 or less at the third atom of thering counted from a nitrogen atom attached to Z, the nitrogen atom beingcounted as the first atom;

each X and Y is independently a carbon atom or a nitrogen atom;

A is a group of atoms necessary to form a 5 or 6 membered hydrocarbonring or heterocyclic ring with X—C;

B is —C(R₀₁)═C(R₀₂)—, —N═C(R₀₂)—, —C(R₀₁)═N—, or —N═N—, provided thateach R₀₁ and R₀₂ is independently a hydrogen atom or a substituent;

X₁-L1-X₂ is a bidentate ligand, provided that each X₁ and X₂ isindependently a carbon atom, a nitrogen atom or an oxygen atom, and thatL1 is a group of atoms necessary to form the bidentate ligand with X₁and X₂;

m1 is an integer of 1 to 3, and m2 is an integer of 0 to 2, providedthat a sum of m1 and m2 is 2 or 3; and

M₁ is a metal element selected from the group consisting of Groups 8 to10 in the periodic table.

-   (2) An organic electroluminescent element material represented by    Formula (1B),

wherein each X and Y is independently a carbon atom or a nitrogen atom;

A is a group of atoms necessary to form a 5 or 6 membered hydrocarbonring or heterocyclic ring with X—C;

B is —C(R₀₁)═C(R₀₂)—, —N═C(R₀₂)—, —C(R₀₁)═N—, or —N═N—, provided thateach R₀₁ and R₀₂ is independently a hydrogen atom or a substituent;

X₁-L1-X₂ is a bidentate ligand, provided that each X₁ and X₂ isindependently a carbon atom, a nitrogen atom or an oxygen atom, and thatL1 is a group of atoms necessary to form the bidentate ligand with X₁and X₂;

m1 is an integer of 1 to 3, and m2 is an integer of 0 to 2, providedthat a sum of m1 and m2 is 2 or 3; and

M₁ is a metal element selected from the group consisting of Groups 8 to10 in the periodic table; and

Zb is a group selected from the group consisting of:

provided that (*) indicates a position which binds to a nitrogen atom.

-   (3) The organic electroluminescent element material of the    above-described item (2), wherein Zb in Formula (1B) has further a    halogen atom.-   (4) An organic electroluminescent element material comprising a    polymer having a partial structure represented by Formula (1B) of    the above-described item (2) in the molecule.-   (5) An organic electroluminescent element material represented by    Formula (2),

wherein R is a substituent having a steric parameter value (Es) of −0.5or less,;

R₁ is a hydrogen atom or a substituent, and n1 is an integer of 1 to 4;

R₂ is a hydrogen atom or a substituent, and n2 is an integer of 1 or 2;

Z₁ is a group of atoms necessary to form a 5 or 6 membered hydrocarbonring or heterocyclic ring with C—C;

Z₂ is a group of atoms necessary to form a hydrocarbon ring or aheterocyclic ring with C—C;

X₁-L1-X₂ is a bidentate ligand, provided that each X₁ and X₂ isindependently a carbon atom, a nitrogen atom or an oxygen atom, and thatL1 is a group of atoms necessary to form the bidentate ligand with X₁and X₂;

m1 is an integer of 1 to 3, and m2 is an integer of 0 to 2, providedthat a sum of m1 and m2 is 2 or 3; and

M₁ is a metal element selected from the group consisting of Groups 8 to10 in the periodic table.

-   (6) The organic electroluminescent element material of the    above-described item (5), wherein in Formula (2), n1 is 2 or more    and a plurality of R₁s forms a ring by binding together.-   (7) The organic electroluminescent element material of the    above-described item (5), wherein R₁ in Formula (2) is an aromatic    hydrocarbon having a substituent.-   (8) The organic electroluminescent element material of the    above-described item (5), wherein R₁ in Formula (2) is an aromatic    heterocylic group or a non aromatic heterocylic group.-   (9) The organic electroluminescent element material of the    above-described item (5), wherein R₁ in Formula (2) is an alkoxy    group or an aryloxy group.-   (10) The organic electroluminescent element material of the    above-described item (5), wherein R₂ in Formula (2) is a    substituent.-   (11) The organic electroluminescent element material of the    above-described item (5), wherein Formula (2) is further represented    by Formula (3),

wherein R is a substituent having a steric parameter value (Es) of −0.5or less,;

R₁ is a hydrogen atom or a substituent, and n1 is an integer of 1 to 4;

each R₂ and R₃ is independently a hydrogen atom or a substituent, n2 isan integer of 1 or 2 and n3 is an integer of 1 to 4;

X₁-L1-X₂ is a bidentate ligand, provided that each X₁ and X₂ isindependently a carbon atom, a nitrogen atom or an oxygen atom, and thatL1 is a group of atoms necessary to form the bidentate ligand with X₁and X₂;

m1 is an integer of 1 to 3, and m2 is an integer of 0 to 2, providedthat a sum of m1 and m2 is 2 or 3; and

M₁ is a metal element selected from the group consisting of Groups 8 to10 in the periodic table.

-   (12) The organic electroluminescent element material of the    above-described item (11), wherein Formula (3) is further    represented by Formula (4),

wherein R is a substituent having a steric parameter value (Es) of −0.5or less,;

R₁ is a hydrogen atom or a substituent, and n1 is an integer of 1 to 4;

each R₂ and R₃ is independently a hydrogen atom or a substituent, n2 isan integer of 1 or 2 and n3 is an integer of 1 to 3;

X₁-L1-X₂ is a bidentate ligand, provided that each X₁ and X₂ isindependently a carbon atom, a nitrogen atom or an oxygen atom, and thatL1 is a group of atoms necessary to form the bidentate ligand with X₁and X₂;

m1 is an integer of 1 to 3, and m2 is an integer of 0 to 2, providedthat a sum of m1 and m2 is 2 or 3; and

M₁ is a metal element selected from the group consisting of Groups 8 to10 in the periodic table.

-   (13) The organic electroluminescent element material of the    above-described item (12), wherein R₃ in Formula (4) is a hydrogen    atom.-   (14) The organic electroluminescent element material of the    above-described item (5), wherein m2 in Formula (2) is 0.-   (15) The organic electroluminescent element material of the    above-described item (5), wherein R in Formula (2) is electron    donative.-   (16) The organic electroluminescent element material of the    above-described item (5) exhibiting a first emission wavelength of    400 to 500 nm.-   (17) An organic electroluminescent element comprising the organic    electroluminescent element material of any one of the    above-described items (1), (2) and (5).-   (18) An organic electroluminescent element comprising an emission    layer as a constituting layer of the element, wherein the emission    layer comprises the organic electroluminescent element material of    the above-described item (5).-   (19) The organic electroluminescent element of the above-described    item (18), wherein the emission layer further comprises:

(i) a carboline derivative; or

(ii) a condensed ring compound having a structure derived fromcarboline, wherein at least one of carbon atoms of a hydrocarbon ring ina carboline ring is substituted with a nitrogen atom.

-   (20) The organic electroluminescent element of the above-described    item (17), comprising a positive hole inhibition layer as a    constituting layer of the element, the positive hole layer    containing:

(i) a carboline derivative; or

(ii) a condensed ring compound having a structure derived fromcarboline, wherein at least one of carbon atoms of a hydrocarbon ring ina carboline ring is substituted with a nitrogen atom.

-   (21) A display device comprising the organic electroluminescent    element of the above-described item (17).-   (22) A lighting device comprising the organic electroluminescent    element of the above-described item (17).

This invention has been able to provide an organic EL element materialfor and an organic EL element having specific properties, and it hasbeen achieved to provide an organic EL element, an illumination deviceand a display device having high emission efficiency and long emissionlife utilizing said organic EL element material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing to show an example of a display deviceconstituted of an organic EL element.

FIG. 2 is a schematic drawing of display section A.

FIG. 3 is an equivalent circuit diagram of an image pixel.

FIG. 4 is a schematic drawing of a full color display device accordingto a passive matrix mode.

FIG. 5 is a schematic drawing of an illumination device.

FIG. 6 is a schematic drawing of an illumination device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In an organic electroluminescent element material of this invention, anorganic EL element material, which is a metal complex having a specificligand, could be obtained by adopting a constitution defined by any oneof the embodiments of the present invention. An organic EL elementhaving high emission efficiency and long emission life could be obtainedby utilizing said organic EL element material. Further, by utilizing theaforesaid organic electroluminescent element, the display devicedescribed above and the illumination device described above each,exhibit high luminance as well as high durability, could be obtained.

In the following, the detail of each constituent element according tothis invention will be successively explained.

Metal complexes related to the organic EL element materials of thepresent invention will now be described.

In view of the foregoing, the inventors of the present inventionconducted diligent investigation and found that by employing organic ELelements incorporating the metal complex represented by each of aboveFormulas (1), (1B), (2) and (3), or Formula (4) as an organic EL elementmaterial, luminescent efficiency and luminescent lifetime are markedlyimproved.

The inventors of the present invention conducted further diligentinvestigation and also discovered that with regard to phenylimidazolederivatives, the stability of the complex varied to a great extentdepending on effects of the substitution position and types of asubstituent to phenylimidazole employed as a mother nucleus, whereby theabove significantly affected the luminescent lifetime.

The inventors of the present invention discovered that as the metalcomplexes according to the present invention, by introducing asubstituent having a specific steric or electronic parameter forimidazole into a heterocyclic ring, an aromatic heterocyclic ring, or anaromatic hydrocarbon ring, luminescent lifetime was markedly extended,which had caused problems for the organic EL element prepared byemploying an organic EL element material which controlled theluminescent wavelength to the shorter wavelength side only byconventional metal complexes for blue, especially by an electronattractive group, whereby compatibility of the luminescent efficiencyand the luminescent lifetime was realized. Further, it was discoveredthat by specifying the substitution position, size and electronicproperties of an aromatic ring-shaped substituent, the lifetime of aluminescent element for blue, exhibiting excellent color purity, wasfurther extended, whereby a significant extension of the luminescentlifetime of organic EL elements was realized.

The concept of the present invention will now be described. Descriptionis made while referring to an example in which an aromatic hydrocarbonring is introduced into the N position of 2-phenylimidazole. Namely, itis common knowledge that the introduction of a phenyl group into the Nposition of 2-phyenylimidazole is difficult in terms of synthesis,compared to the case in which a straight chain alkyl group is introducedinto the N position. In addition, it has been featured that metalcomplexes employing the above ligand emit luminescence of a longerwavelength to broaden the waveform. The above suggests that theconjugated system is not cut off irrespective of the fact that thephenyl group on the N position is bonded via a nitrogen atom. It ispossible to describe broadening of the luminescent wavelength due to asignificant increase in probability of the presence of the vibrationlevel due to rotation, compared to the ligand of the N-methylatedcompound. This assumption is supported by the molecular orbitalcalculation based on GAUSSIAN.

The inventors of the present invention conducted diligent investigationand achieved the present invention by discovering the following effectsvia introduction of a cyclic substituent having a bulky substituent inthe ortho position onto the N position of phenylimidazole;

1) an increase in twist of the phenyl group to result in cutting of theconjugated system and in shortening the wavelength,

2) a decrease in probability of the vibration level due to retardationof free rotation via the presence of the bulky substituent,

3) significant enhancement of stability of molecules via protection ofthe N position, which tends to be oxidized, employing the bulkysubstituent, and

4) achieved compatibility of wavelength shortening with lifetimeextension by combining the size of the substituted atom and theelectronic effect.

Further, even in a ligand having the mother nucleus according to thepresent invention, by introducing an auxiliary ligand to be combined ora substituent itself which results in a longer wavelength, it ispossible to control the emission wavelength of metal complexes withinthe desired region. Accordingly, it is possible to start a moleculardesign which provides a function to control the luminescence wavelengthof metal complexes into the longer wavelength region (green-red) fromthe point in which Formulas (1), (1B), (2) or (3) according to thepresent invention, or Formula (4) is employed as a starting point forthe basic skeleton design.

(Ligands)

In the metal complexes according to the present invention, for example,when description is made employing above Formula (1), when m1>m2, thepartial structure represented in parenthesis having m1 or the partialstructure represented by the tautomer is called a primary ligand, whilethe partial structure represented in parenthesis having m2 or thetautomer is called a secondary ligand.

In the present invention, as represented by Formula (1), the above metalcomplexes are composed of a primary ligand or its tautomer as well as asecondary ligand or its tautomer. However, as described below, m2=0 isallowed, namely all the ligands of the above metal complexes arecomposed of only the partial structure represented by the primary ligandor its tautomer.

Further, if desired, incorporated may be ligands (also calledcoordination compounds) well known as a so-called ligand by a personskilled in the art which is employed to form conventional metalcomplexes.

In view of achieving preferable results in desired effects of thepresent invention, the ligand in complexes is composed of 1 or 2 types,but is preferably composed of only one type.

Ligands employed in conventional metal complexes known in the artinclude various types. Examples include ligands (for example, halogenligands, being preferably a chlorine ligand, and nitrogen containingheterocyclic ligands such as bipyridyl or phenanthroline, and diketoneligands) described, for example, in H. Yersin, “Photochemistry andPhotophysics of Coordination Compounds” Springer-Verlag Co., publishedin 1987, and in Akio Yamamoto, “Yuki Kinzoku Kagaku -Kiso to Oyo-(Organic Metal Chemistry -Bases and Applications-)” Shokabo Sha,published in 1982.

(Transition Metal Elements of Groups 8-10 of the Periodic Table ofElements)

Employed as a metal used to form the metal complexes represented byFormulas (1), (1B), (2) or (3) according to the present invention, orFormula (4) are the transition metal elements (also simply referred toas transition metals) of Groups 8-10 of the periodic table. Of these,iridium and platinum are listed as a preferable transition metalelement.

Further, by employing such organic EL element materials, it becamepossible to provide organic EL elements which exhibit high luminescentefficiency and long luminescent lifetime, a lighting device and adisplay device.

Each of the constituting components according to the present inventionwill now be successively detailed.

Metal complexes which are organic EL element materials of the presentinvention will be described first.

Preferred as a layer incorporating the metal complexes represented byabove Formulas (1), (1B), (2) or (3) according to the present invention,or Formula (4) is an emission layer and/or an electron inhibition layer.Further, when incorporated in the emission layer, by employing them as aemission dopant in the emission layer, it is possible to achieve anincrease in the quantum efficiency (to realize high luminance) to betaken out and the extension of luminescent lifetime of the organic ELelements of the present invention.

The metal complexes represented by above Formula (1), (1B), (2) or (3),according to the present invention, or Formula (4) will be describednext.

In Formula (1), Z represents a hydrocarbon ring or a heterocyclic ring(including each of the tautomers) in which a substituent of a stericparameter (being an Es value) of at most −0.5 is bound to at least oneatom located in the third position from the nitrogen atom to be bound.“Es value”, as described herein, refers to a steric parameter derivedfrom chemical reactivity. It is possible to describe that a decrease inthis value indicates that the substituent becomes spatially more bulky.

Es value will now be described. It is common knowledge that in ahydrolysis reaction of esters under acidic conditions, effects for theprogress of the reaction may be considered to be only caused by thesteric hindrance. Based on this, the value which numerically expressesthe steric hindrance is Es value.

Es value of substituent X may be obtainable as follows. Reaction rateconstant kX of the following chemical reaction in which α-positionmono-substituted acetate, which is derived from α-positionmono-substituted acetic acid prepared by substituting one hydrogen atomof the methyl group of acetic acid with substituent X, undergoeshydrolysis under acidic conditions, is obtained.

X—CH₂COORX+H₂O→X—CH₂COOH+RXOH

Reaction rate constant kH of the following reaction (RX is the same asRY) in which acetate corresponding to the above α-positionmono-substituted acetate undergoes hydrolysis under acetic conditions,is also obtained.

CH₃COORY+H₂O→CH₃COOH+RYOH

Subsequently, Es is obtained via the following formula.

Es=log(kX/kH)

The reaction rate decreases due to steric hindrance of substituent X. Asa result, since kX<kH is held, Es value commonly becomes negative. Inpractice, when Es value is obtained, two reaction rate constants, namelykX and kH, are determined and it is calculated based on the aboveformula.

Specific examples of Es value are detailed in Unger, S. H., Hansch, C.,Prog. Phys. Org. Chem. 12, 91 (1976). Further, specific numerical valuesare also described in “Yakubutsu no Kozo Kassei Sokan (StructuralActivity Correlation)” (Kagaku no Ryoiki Zokan No. 122, Nanko Do), and“American Chemical Society Professional Reference Book, ‘Exploring QSAR’p. 81, Table 3-3”. Table 1 below shows some of them.

TABLE 1 Substituent Es Value Substituent Es Value H 0 CH₂OCH₃ −1.43 F−0.46 CH₂NO₂ −2.71 Cl −0.97 CH₂COCH₃ −1.99 Br −1.16 CHF₂ −1.91 I −1.4CHCl₂ −2.78 CH₃ −1.24 CHBr₂ −3.1 C₂H₅ −1.31 CHOHCH₃ −1.15 n-C₃H₇ −1.6CF₃ −2.4 n-C₄H₉ −1.63 CCl₃ −3.3 i-C₄H₉ −2.17 CBr₃ −3.67 s-C₄H₉ −2.37C(C₆H₅)₃ −5.92 t-C₄H₉ −2.78 CHCH₃ −2.84 cyclo-C₄H₇ −1.3 CN −0.51 n-C₅H₁₁−1.64 OH −0.55 i-C₅H₁₁ −1.59 OCH₃ −0.55 CH(C₂H₅₎ −3.22 SH −1.07cyclo-C₆H₁₁ −2.03 SCH₃ −1.07 CH₂F −1.48 SF₅ −2.91 CH₂Cl −1.48 NH₂ −0.61CH₂Br −1.51 CH₂I −1.61 CH₂OH −1.21

Further, it should be noted that the Es value, which is defined in thepresent invention, is not determined while a methyl group is 0, but isdetermined while a hydrogen atom to be 0, whereby the Es value of thepresent invention is a value which is obtained by subtracting 1.24 fromthe Es value determined while a methyl group is 0.

In one of the embodiments of n the present invention, the Es value iscommonly at most −0.5, is preferably between −7.0 and −0.6, but is mostpreferably between −7.0 and −1.0.

Further, in the present invention, in the case of a substituent at asteric parameter (being a Es value) of at most −0.5, for example, in thecase in which keto-enol tautomers are present in R and R′, the Es valueof the keto portion is determined via conversion as an enol isomer. Incases in which other tautomers are present, Es values are determinedbased on the same conversion method. Further, a substituent at an Esvalue of at most −0.5 is preferably an electron donative group in termsof electronic effects. In the present invention, “a substituent iselectron donating” means that Hammett σp value described below is anegative value and such substituent has a larger tendency to donateelectrons to the bonded atoms when compared with a

Specific examples of an electron-donating substituent include: ahydroxyl group, a methoxy group, an acetyloxy group, an amino group, adimethylamino group, an acetylamino group, alkyl groups (for example, amethyl group, an ethyl group, a propyl group and tert-butyl), and arylgroups (for example, a phenyl group) . The following literatures can bereferred to for Hammett σp value, for example.

<<Hammett σp Value>>

Hammett σp value of the present invention represents Hammett substituentconstant σp. Hammett σp value was determined from the electronic effectof the substituent exerted on hydrolysis of ethyl benzoate by Hammett etal. Groups shown in, for example, “Structure-activity relationship of adrug” (Nankodo Co., Ltd.: 1979), or “Substituent Constants forCorrelation Analysis in chemistry and biology” (C. Hansch and A. Leo,John Wiley&Sons, New York, 1979) can be cited.

Preferred examples of Z in Formula (1) are listed below. Other than thelisted examples below, Z may have substituent(s), whereby Z is notlimited to these examples. Incidentally, * represents a bindingposition.

In Formula (1), Y represents a carbon atom or a nitrogen atom, but ispreferably a carbon atom. B represents —C(R₀₁)═C(R₀₂)—, —N═C(R₀₂)—,—C(R₀₁)═N—, or —N═N—.

Preferred examples of nitrogen-containing heterocyclic groupsincorporating Y include a 2-imidazoyl group, a 2-(1,3,4-triazolyl)group, a 2-(1,3,5-triazolyl) group, and a 2-tetrazolyl group. Of thesenitrogen-containing heterocyclic groups, the 2-imidazolyl group is mostpreferred.

R₀₁ and R₀₂ each represents a hydrogen atom or a substituent. Examplesof such a substituent include an alkyl group (for example, a methylgroup, an ethyl group, a propyl group, an isopropyl group, a tert-butylgroup, a pentyl group, a hexyl group, an octyl group, a dodecyl group, atridecyl group, a tetradecyl group, and a pentadecyl group), acycloalkyl group (for example, a cyclopentyl group and a cyclohexylgroup), an alkenyl group (for example, a vinyl group and an allylgroup), an alkynyl group (for example, an ethynyl group and a propargylgroup), an aromatic hydrocarbon ring group (also called an aromaticcarbon ring group or an aryl group such as a phenyl group, ap-chlorophenyl group, a mesityl group, a tolyl group, a xylyl group, anaphthyl group, an anthryl group, an azulenyl group, an acenaphthenylgroup, fluorenyl group, a phenanthryl group, an indenyl group, a pyrenylgroup, or a biphenyl group), an aromatic heterocyclic group (forexample, a pyridyl group, a pyrimidinyl group, a furyl group, a pyrrolylgroup, an imidazolyl group, a benzimidazolyl group, a pyrazolyl group, apiradinyl group, a triazolyl group (for example, a 1,2,4-triazole-1-ylgroup and a 1,2,3-triazole-1-yl group), an oxazolyl group, abenzoxazolyl group, a thiazolyl group, an isooxazolyl group, anisothiazolyl group, a furazanyl group, a thienyl group, a quinolylgroup, a benzofuryl group, a dibenzofuryl group, a benzothienyl group, adibenzothienyl group, an indolyl group, a carbazolyl group, a carbolynylgroup, a diazacarbazoyl group (which shows that one of the carbon atomswhich constitute a carboline ring of the above carbolinyl group isreplaced with a nitrogen atom), a quinoxythalinyl group, a pyridazinylgroup, a triazinyl group, a quinazolinyl group, a phthalazinyl group), aheterocyclic group (for example, a pyrrolidinyl group, an imidazolidylgroup, a morpholyl group, and an oxazolidyl group), an alkoxy group (forexample, a methoxy group, an ethoxy group, a propyloxy group, apentyloxy group, a hexyloxy group, an octyloxy group, and a dodecyloxygroup), a cycloalkoxy group (for example, a cyclopentyloxy group and acyclohexyloxy group), an aryloxy group (for example, a phenoxy group anda naphthyloxy group), an alkylthio group (for example, a methylthiogropup, an ethylthio group, a propylthio group, a pentylthio group, ahexylthio group, an octylthio group, and a dodecylthio group), acycloalkylthio group (for example, a cyclopentylthio group and acyclohexylthio group), an arylthio group (for example, a phenylthiogroup and a naphthylthio group), an alkoxycarbonyl group (for example, amethyloxycarbonyl group, an ethyloxycarbonyl group, a butyloxycarbonylgroup, an octyloxycarbonyl group, and a dodecyloxycarbonyl group), anaryloxycarbonyl group (for example, a phenyloxycarbonyl group and anaphthyloxycarbonyl group), a sulfamoyl group (for example, anaminosulfonyl group, a methylaminosulfonyl group, adimethylaminosulfonyl group, a butylaminosulfonyl group, ahexylaminosulfonyl group, a cyclohexylaminosulfonyl group, anoctylaminosulfonyl group, a dodecylaminosulfonyl group, aphenylaminosulfonyl group, a naphthylaminosulfonyl group, and a2-pyridylaminosulfonyl group), an acyl group (for example, an acetylgroup, an ethylcarbonyl group, a propylcarbonyl group, a pentylcarbonylgroup, a cyclohexylcarbonyl group, an octylcarbonyl group, a2-ethylhexylcarbonyl group, a dodecylcarbonyl group, a phenylcarbonylgroup, a naphthylcarbonyl group, a pyridylcarbonyl group), an acyloxygroup (for example, an acetyloxy group, an ethylcarbonyloxy group, abutylcarbonyloxy group, an octylcarbonyloxy group, a dodecylcarbonyloxygroup, and a phenylcarbonyloxy group), an amido group (for example, amethylcarbonylamino group, an ethylcarbonylamino group, adimethylcarbonylamino group, a propylcarbonylamino gropup, apentylcarbonylamino group, a cyclohexylcarbonylamino group, a2-ethylhexylcarbonylamino group, an octylcarbonylamino group, adodecylcarbonylamino group, a phenylcarbonylamino group, and anaphthylcarbonylamino group), a carbamoyl group (for example, anaminocarbonyl group, a methylaminocarbonyl group, adimethylaminocarbonyl group, a propylaminocarbonyl group, apentylaminocarbonyl group, a cyclohexylaminocarbonyl group, anoctylaminocarbonyl group, a 2-ethylhexylaminocarbonyl group, adodecylaminocarbonyl group, a phenylaminocarbonyl group, anaphthylaminocarbonyl group, and a 2-pyridylaminocarbonyl group), anureido group (for example, a methylureido group, an ethylureido group, apentylureido group, a cyclohexylureido group, an octylureido group, adodecylureido group, a phenylureido group, a naphthylureido group, and a2-pyridylaminoureido group), a sulfinyl group (for example, amethylsulfinyl group, an ethylsulfinyl group, a butylsulfinyl group, acyclohexylsulfinyl group, a 2-ethylhexylsulfinyl group, adocecylsulfinyl group, a phenylsulfinyl group, a naphthylsulfinyl group,and a 2-pyridylsulfinyl group), an alkylsulfonyl group (for example, amethylsulfonyl group, an ethylsulfonyl group, a butylsulfinyl group, acyclohexylsulfonyl group, a 2-ethylhexylsulfonyl group, and adodecylsulfonyl group), an arylsulfonyl group or a heteroarylsulfonylgroup (for example, a phenylsulfonyl group, a naphthylsulfonyl group,and a 2-pyridylsulfonyl group), an amino group (for example, an aminogroup, an ethylamino group, a dimethylamino group, a butylamino group, acyclopentylamino group, a 2-ethylhexylamino group, a dodecylamino group,an anilino group, a cyclopentylamino group, a 2-ethylhexylamino group, adodecylamino group, an anilino group, a naphthylamino group, and a2-pyridylamino group), a halogen atom (for example, a fluorine atom, achlorine atom, and a bromine atom), a fluorinated hydrocarbon group (forexample, a fluoromethyl group, a trifluoromethyl group, apentafluoroethyl group, and a pentafluorophenyl group), a cyano group, anitro group, a hydroxyl group, a mercapto group, and a silyl group (forexample, a trimethylsilyl group, a triisopropylsilyl group, atriphenylsilyl group, and a phenyldiethylsilyl group). Thesesubstituents may be substituted with the above substituents. Further,these substituents may be bound together to form a ring.

In the hydrocarbon ring or the heterocyclic group represented by A-C—Xof Formula (1), X represents either a carbon atom or a nitrogen atom,but is preferably a carbon atom.

When the hydrocarbon ring represented by A-C—X is an aromatichydrocarbon ring, it is one in which one hydrogen atom at an optionalposition is removed from the 4n+2π based aromatic hydrocarbon compound,and specific examples include a phenyl group, a 1-naphthyl group, a2-naphthyl group, a 9-anthryl group, a 1-anthryl group, a 9-phenanthrylgroup, a 2-triphenylenyl group, and a 3-perylenyl group. Further, theabove hydrocarbon ring group may be substituted, for example with thesubstituent described in R₀₁, and further, may form a condensed ring(for example, a 9-pyrenyl group which is prepared by condensing ahydrocarbon ring to a 9-phenanthryl group or a 8-quinolyl group which isprepared by condensing a heterocycle to a phenyl group).

When the heterocyclic group, represented by A-C—X, is an aromaticheterocyclic group, it is preferable that in the above aromaticheterocyclic group, at least one side contacting position of the portionbound to the nitrogen-containing aromatic heterocycle is a carbon atom,and though no particular limitation is made for the 4n+2π based aromaticgroup, both contacting positions of the portion bound to thenitrogen-containing aromatic heterocycle are carbon atoms. Specificexamples include a 3-pyridyl group, a 5-pyrimidyl group, a 4-pyridadylgroup, a 5-pyridadyl group, a 4-isooxazolyl group, a 4-isothiazolylgroup, a 4-pyrazolyl group, a 3-pyrrolo group, a 3-furyl group, and a3-thienyl group. Further, the above heterocycle may be substituted, forexample, with the substituent described in R₀₁, and still further, mayform a condensed ring.

In Formula (1), X₁-L1-X₂ represents a bidentate ligand, and X₁ and X₂each independently represents a carbon atom, a nitrogen atom, or anoxygen atom. L1 represents a group of atoms which forms a bidentateligand together with X₂. Specific examples of the bidentate ligandrepresented by X₁-L1-X₂ include substituted or unsubstitutedphenylpyridine, phenylpyrazole, phenylimidazole, phenyltriazole,phenyltetrazole, pyrazabole, acetylacetone, and picolinic acid. “m1”represents an integer of 1, 2, or 3, while m2 represents an integer of0, 1, or 2, wherein m1 plus m2 is 2 or 3. Of these, the case in which m2is 0 is preferred.

In Formula (1B), each X and Y is independently a carbon atom or anitrogen atom;

A is a group of atoms necessary to form a 5 or 6 membered hydrocarbonring or heterocyclic ring with X—C;

B is —C(R₀₁)═C(R₀₂)—, —N═C(R₀₂)—, —C(R₀₁)═N—, or —N═N—, provided thateach R₀₁ and R₀₂ is independently a hydrogen atom or a substituent;

X₁-L1-X₂ is a bidentate ligand, provided that each X₁ and X₂ isindependently a carbon atom, a nitrogen atom or an oxygen atom, and thatL1 is a group of atoms necessary to form the bidentate ligand with X₁and X₂;

m1 is an integer of 1 to 3, and m2 is an integer of 0 to 2, providedthat a sum of m1 and m2 is 2 or 3; and

M₁ is a metal element selected from the group consisting of Groups 8 to10 in the periodic table; and

Zb is a group selected from the group for the item (2) described above.

In Formula (2), R represents a substituent at a steric parameter (Esvalue) of at most −0.5, which is located in the ortho position of thering composed of Z₂ bound to the nitrogen atom of the imidazole ring. Esvalues are as detailed in Formula (1). Specific examples of R includesubstituents shown in Table 1 in the description of Formula (1).

R₁ represents a hydrogen atom or a substituent, and n1 represents aninteger of 1-4. R₂ represents a hydrogen atom or a substituent and n2represents an integer of 1 or 2.

Z₂ represents a hydrocarbon ring or a heterocycle, or a group of atomswhich is necessary to form a tautomer thereof. The above group of atomsmay further have substituent(s), and examples of the substituents are asdefined for R₀₁ of Formula (1). When a plurality of substituents isfurther present, the plurality of substituents may be bound togetherother to form a ring. Preferable specific examples include substituentslisted as Z of Formula (1).

In Formula (2), Z₁ represents a group of atoms, which is necessary toform a 5- to 6-membered hydrocarbon ring or heterocycle together withC—C. Preferred as the hydrocarbon rings are aromatic hydrocarbon rings,while preferred as heterocycles are aromatic heterocycles.

The aromatic hydrocarbon group is one in which one hydrogen atom at anoptional position is removed from a 4n+2 based aromatic hydrocarboncompound, and specific examples include a phenyl group, a 1-naphthylgroup, a 2-naphthyl group, a 9-antholyl group, a 1-antholyl group, a9-phenantholyl group, a 2-triphenylenyl group, and a 3-perylenyl group.The above aromatic hydrocarbon group may further be substituted, forexample, with the substituent described in R₀₁ of Formula (1), and acondensed ring (for example, a 9-pyrenyl group prepared by condensing a9-phenantolyl group to a hydrocarbon ring and a 8-quinolyl groupprepared by condensing a heterocycle to a phenyl group, may be formed.

Aromatic heterocyclic groups are not particularly limited as long as atleast one side contacting position of the portion bound to anitrogen-containing heterocycle is a carbon atom and the above groupsare 4n+2π based aromatic substituents, but dual side contactingpositions of the portion bound to the nitrogen-containing aromaticheterocycle are carbon atoms. Specifically listed are a 3-pyridyl group,a 5-pyrimidyl group, a 4-pyridadyl group, a 4-isooxazoyl group, a4-isothiazolyl group, a 4-pyrazolyl group, a 3-pyrrolo group, a 3-furylgroup, and a 3-thienyl group. The above aromatic heterocycle may furtherbe substituted with the substituent described in R₀₁ of Formula (1), andmay further form a condensed ring.

In Formula (2), R₁ and R₂ each represents a hydrogen atom or asubstituent, while n1 represents an integer of 1-4 and n2 represents aninteger of 1-2. However, when a plurality of substituents is present atR₁ or R₂, R₁ and R₂ each may be the same or different. Further, aplurality of substituents of R₁ or R₂ may be bound together to form aring.

In Formula (2), X₁-L1-X₂ represents a bidentate ligand, and X₁ and X₂each independently represents a carbon atom, a nitrogen atom, or anoxygen atom. L1 represents a group of atoms which forms a bidentateligand together with X₂. Specific examples of the bidentate ligandrepresented by X₁-L1-X₂ include substituted or unsubstitutedphenylpyridine, phenylpyrazole, phenylimidazole, phenyltriazole,phenyltetrazole, pyrazabole, acetylacetone, and picolinic acid. “m1”represents an integer of 1, 2, or 3, while m2 represents an integer of0, 1, or 2, wherein m1 plus m2 is 2 or 3. Of these, the case in which m2is 0 is preferred.

In Formula (3), R represents a substituent at a steric parameter (Esvalue) of at most −0.5. Es values are as detailed in Formula (1).Specific examples of R include substituents shown in Table 1 in thedescription of Formula (1) .

R₁ and R₂ each represents a hydrogen atom or a substituent, and isdefined as the description in Formula (2). R₃ represents a hydrogen atomor a substituent, while n3 represents an integer of 1-4. However, when aplurality of substituents is present, each R₃ may be the same ordifferent. Further, a plurality of R₃ may be bound together to form aring.

In Formula (3), X₁-L1-X₂ represents a bidentate ligand, and X₁ and X₂each independently represents a carbon atom, a nitrogen atom, or anoxygen atom. L1 represents a group of atoms which forms a bidentateligand together with X₂. Specific examples of the bidentate ligandrepresented by X₁-L1-X₂ are as those described in Formula (2). “m1”represents an integer of 1, 2, or 3, while m2 represents an integer of0, 1, or 2, wherein m1 plus m2 is 2 or 3. Of these, the case in which m2is 0 is preferred.

In Formula (4), R represents a substituent at a steric parameter (Esvalue) of at most −0.5. Es values are as detailed in Formula (1).Specific examples of R include substituents shown in Table 1 in thedescription of Formula (1).

R₁ and R₂ each represents a hydrogen atom or a substituent, and isdefined as the description in Formula (2). R₃ represents a hydrogen atomor a substituent, while n3 represents an integer of 1-4. However, when aplurality of substituent R₃ is present, each R₃ may be the same ordifferent. Further, a plurality of R₃ may be bound together to form aring.

In Formula (4), X₁-L1-X₂ represents a bidentate ligand, and X₁ and X₂each independently represents a carbon atom, a nitrogen atom, or anoxygen atom. L1 represents a group of atoms which forms a bidentateligand together with X₂. Specific examples of the bidentate ligandrepresented by X₁-L1-X₂ are as those described in Formula (2). “m1”represents an integer of 1, 2, or 3, while m2 represents an integer of0, 1, or 2, wherein m1 plus m2 is 2 or 3. Of these, the case in which m2is 0 is preferred.

In Formulas (2)-(4), R and R′ are preferably electron donative groups.The electron donative groups are as those described in Formula (1).

In Formulas (1)-(4), central metal M₁ represents a metal in Groups 8-10of the periodical table of elements. Of these, iridium or platinum isparticularly preferred.

The specific examples represented by above Formulas (1), (1B), (2), and(3) according to the present invention, of Formula (4) will now belisted, however the present invention is not limited thereto.

Metal complexes according to an organic EL element material of thisinvention can be synthesized by applying a method described in such asOrganic Letter, vol. 3, No. 16, pp. 2579-2581 (2001), InorganicChemistry vol. 30, No. 8, pp. 1685-1687 (1991), J. Am. Chem. Soc., vol.123, p. 4304 (2001), Inorganic Chemistry vol. 40, No. 7, pp. 1704-1711(2001), Inorganic Chemistry vol. 41, No. 12, pp. 3055-3066 (2002), NewJournal of Chemistry, vol. 26, p. 1171 (2002), European Journal ofOrganic Chemistry Vol. 4, pp. 95-709 (12004), and reference documentsdescribed in these documents.

Synthesis examples of the representative compounds will now bedescribed.

Further, the structure of the synthesized compound was confirmed via1H-NMR and MS spectra.

SYNTHESIS EXAMPLE 1 Synthesis of 1-Phenylimidazole (Comparative Example)

Charged into a reaction vessel was 3.30 g (0.01734 mol) ofphenanthroline monohydrate, the moisture of which was removed viaheating while reducing pressure. After cooling, 1.32 g (0.006936 mol) ofcopper iodide, 10 g (0.06936 mol) of 2-phenylimidazole, 7.0 g of 4Amolecular sieve, 20.1 g (0.1457 mol) of potassium carbonate, 50 ml ofdimethylformamide, and 14.9 g (0.07283 mol) of iodobenzene were added,followed by reaction for 10 hours while refluxed. Thereafter,iodobenzene was further added and the reaction was performed at areaction temperature of about 160° C. for 15 hours, while distilling offdimethylformamide. After cooling the reaction products, the resultingsolution was diluted with ethyl acetate, and insoluble compounds werecollected via filtration, followed by washing with well water. Afterconcentrating the organic layer, the targeted compound was isolated viasilica gel column chromatography (in which ethyl acetate/hexane was1/4), whereby 9.52 g (65.3%) of 1-phenylimidazole was obtained.

SYNTHESIS EXAMPLE 2 Synthesis of 1-Phenylimidazole (Comparative Example)

Reaction was performed in the same manner as Synthesis Example 1, exceptthat iodobenzene employed in Synthesis Example 1 was replaced withmesityl iodide. However, no reaction occurred, and then no targeted1-phenylimidazole was obtained.

SYNTHESIS EXAMPLE 3 Synthesis of2-Phenyl-1-(2,4,6-trimethylphenyl)-1H-imidazole (1) Synthesis of1-(2,4,6-trimethylphenyl)1H-imidazole

Charged into a reaction vessel were 15.9 g (0.08813 mol) ofphenanthroline, which was dehydrated in the same manner as SynthesisExample 1, 7.2 g (0.03781 mol) of copper iodide, 102.3 g (0.7402 mol) ofpotassium carbonate, 25.0 g of 4A molecular sieve, 24.0 g (0.3525 mol)of dimethylformamide, 25 g of mesityl iodide, and 78 g of mesitylbromide. When the interior temperature reached nearly 150° C.,dimethylacetamide was distilled off, and reaction was performed for 14hours at an interior temperate of approximately 170° C. Thepost-treatment and separation were carried out in the same manner as forSynthesis Example 1, whereby 35.4 g (54.9%) of targeted1-(2,4,6-trimethylphenyl)-1H-imidazole was obtained.

(2) Synthesis of 2-Bromo-1-(2,4,6-trimethylphenyl)-1H-imidazole

Charged into a reaction vessel was 1-mesitylimidazole, and subsequently,under a flow of nitrogen, 500 ml of dehydrated tetrahydrofuran wasadded. Further, under a flow of nitrogen, the interior temperature waslowered to at most −60° C., and 180 ml n-butyl lithium (being a hexanesolution at a concentration of 1.57 mol) was dripped.

Thereafter, after elevating the interior temperature to −30° C. over 30minutes, the interior temperature was again lowered to at most −60° C.,and 14.5 ml of bromine was dripped. After the dripping, the innertemperature was elevated to room temperature. Thereafter, a 5% aqueoussodium thiosulfate solution, an aqueous sodium hydrogencarbonatesolution, and ethyl acetate were added. After separation of the organiclayer followed by concentration, the targeted compound was isolated viasilica gel column chromatography (in which ethyl acetate/hexane was2/3), whereby 49.7 g (69.8%) of2-bromo-1-(2,4,6-trimethylphenyl)-1H-imidazole was obtained.

(3) Synthesis of 2-Phenyl-1-(2,4,6-trimethylphenyl)-1H-imidazole

After stirring 6.5 g (0.01131 mol) of bis(dibenzylideneacetone)palladium, 6.3 g of1,1-bis(diphenylphosphino)ferrocene, and 30 ml of ethylene glycoldimethyl ether at 50° C. for 30 minutes under a flow of nitrogen, 50.0 g(0.1885 mol) of 2-bromo-1-(2,4,6-trimethylphenyl)-1H-imidazole, 27.6 gof phenylboronic acid, and 1.3 L of ethylene glycol dimethyl ether wereadded. Further, an aqueous solution prepared by dissolving 62.5 g(0.4526 mol) of potassium carbonate in 300 ml of water was added.Further, under a flow of nitrogen, reaction was performed for 12 hourswhile maintaining the interior temperature at approximately 80° C. Aftercooling the reaction products, the solution was diluted with ethylacetate. After collecting insoluble compounds via filtration, washingwas carried out employing well water. After concentrating the organiclayer, the targeted compound was isolated via silica gel columnchromatography (in which ethyl acetate/hexane was 1/4), whereby 30.6 g(61.8%) of targeted 2-phenyl-1-(2,4,6-trimethylphenyl)-1H-imidazole wasobtained.

Synthesis of Exemplified Compound (154)

Under a nitrogen atmosphere, 8.1 g (0.02297 mol) of iridium trichloridetrihydrate and 100 ml of water were added to a solution prepared bydissolving 18 g (0.06861 mol) of2-phenyl-(2,4,6-trimethylphenyl)-1H-imidazole in 350 ml of2-ethoxymethanol, and the resulting mixture was refluxed for 5 hoursunder a nitrogen atmosphere. The reaction liquor was cooled, followed bythe addition of 500 ml of methanol, and deposited crystals werecollected via filtration. The resulting crystals were washed withmethanol and subsequently dried, whereby 15.2 g (at a yield of 88.4%) ofComplex A was obtained.

Under a nitrogen atmosphere, 14.5 g (0.00966 mol) of Complex A and 14.5g of sodium carbonate were suspended into 350 ml of 2-ethoxyethanol.Subsequently, 3.9 g (0.03895 mol) of acetylacetone was added to theabove suspension and the resulting mixture was refluxed for two hoursunder a nitrogen atmosphere. After cooling the reaction liquor, sodiumcarbonate and inorganic salts were removed via vacuum filtration. Afterconcentrating solvents under vacuum, 1 L of water was added to theresulting solids to form a suspension, followed by collection of solidsvia filtration. The resulting crystals were washed with a solutionprepared by blending methanol and water at a ratio of 1/1 andsubsequently dried, whereby 14.7 g (at a yield of 93.6%) of Complex Bwas obtained.

Under a nitrogen atmosphere, 7.5 g (0.009214 mol) of Complex B and 6.0 g(0.02287 mol) of 2-phenyl-(2,4,6-trimethylphenyl)-1H-imidazole weredispersed into 400 ml of glycerin. Under a nitrogen atmosphere, theresulting mixture underwent reaction for two hours at a reactiontemperature of 150-160° C., and the reaction was terminated uponconfirmation of the absence of Complex B. The reaction liquor wascooled, followed by the addition of 500 ml of methanol, and furtherfollowed by collection of deposited crystals via filtration. Theresulting crystals were further washed with methanol and dried, whereby7.1 g (at a yield of 78.9%) as a crude product was obtained. Theresulting crude product was dissolved in a small amount of methylene,followed by purification (methylene chloride) employing silica gelcolumn chromatography, whereby 6.5 g (at a yield of 72.2%) ofExemplified Compound (154) was obtained.

The wavelength of phosphorescence of Exemplified Compound (154) in asolution was determined employing F-4500, produced by Hitachi, Ltd.,resulting in 466 nm (in 2-methyltetrahydrofuran).

<Application of Organic EL Element Material Containing Metal Complex toOrganic EL Element>

In the case of preparing an organic EL element by utilizing an organicEL element material of this invention, said material is preferablyutilized in an emission layer or an electron inhibition layer amongconstituent layers (details will be described later) of the organic ELelement. Further, the material is preferably utilized as an emissiondopant in an emission layer as described above.

(Emission Host and Emission Dopant)

A mixing ratio of an emission dopant against an emission host as aprimary component in an emission layer, is preferably adjusted to arange of 0.1-30 weight %.

However, plural types of compounds may be utilized in combination as anemission dopant, and the partner to be mixed may be a metal complexhaving a different structure, and a phosphorescent dopant or afluorescent dopant having other structures.

Here, a dopant (such as a phosphorescent dopant and a fluorescentdopant) which may be utilized together with a metal complex employed asan emission dopant will be described. An emission dopant is roughlyclassified into two types, that is, a fluorescent dopant which emitsfluorescence and a phosphorescent dopant which emits phosphorescence.

A typical example of the former (a fluorescent dopant) includes coumarintype dye, pyran type dye, cyanine type dye, chroconium type dye,squalium type dye, oxobenzanthracene type dye, fluorescein type dye,rhodamine type dye, pyrylium type dye, perylene type dye, stilbene typedye, polythiophene type dye or rare earth complex type fluorescentsubstances.

A typical example of the latter (a phosphorescent dopant) is preferablya complex type compound containing metal of the 8th-10th groups of theperiodic table, more preferably an iridium compound and an osmiumcompound and most preferable among them is an iridium compound.

Specifically, listed are compounds described in the following patentpublication:

Such as WO 00/70655, JP-A Nos. 2002-280178, 2001-181616, 2002-280179,2001-181617, 2002-280180, 2001-247859, 2002-299060, 2001-313178,2002-302671, 2001-345183 and 2002-324679, WO 02/15645, JP-A Nos.2002-332291, 2002-50484, 2002-322292 and 2002-83684, JapaneseTranslation of PCT International Application Publication No.2002-540572, JP-A Nos. 2002-117978, 2002-338588, 2002-170684 and2002-352960, WO 01/93642 pamphlet, JP-A Nos. 2002-50483, 2002-100476,2002-173674, 2002-359082, 2002-175884, 2002-363552, 2002-184582 and2003-7469, Japanese Translation of PCT International ApplicationPublication No. 2002-525808, JP-A 2003-7471, Japanese Translation of PCTInternational Application Publication No. 2002-525833, JP-A Nos.2003-31366, 2002-226495, 2002-234894, 2002-235076, 2002-241751,2001-319779, 2001-319780, 2002-62824, 2002-100474, 2002-203679,2002-343572 and 2002-203678.

A part of examples thereof will be shown below.

(Emission Hosts)

A host compound, employed in the present invention, refers to acompound, among those incorporated in the emission layer, which resultsin a phosphorescent quantum yield of less than 0.01 during emittingphosphorescence.

Structures of the emission host employed in the present invention arenot particularly limited. Representative compounds include those havinga basic skeleton such as carbazole derivatives, triarylaminederivatives, aromatic borane derivatives, nitrogen-containingheterocyclic compounds, thiophene derivatives, furan derivatives, oroligoarylene compounds, or derivatives having a ring structure in whichat least one of the carbon atoms of the hydrocarbon ring, whichconstitutes carboline derivatives and the carboline ring of the abovecarboline derivatives, is substituted with a nitrogen atom. Of these,preferably employed are derivatives having a ring structure in whichcarbazole derivatives carboline derivatives or the hydrocarbon ringconstituting carbazole derivatives and carboline derivatives or thecarboline ring of the above carboline derivatives is substituted with anitrogen atom. Of these, derivatives are preferably employed which havea structure in which at least one carbon atom of carbazole derivatives,and carboline derivatives, and the hydrocarbon ring constituting thecarboline ring of the above carboline derivatives.

Specific examples of emission hosts will now be listed, however thepresent invention is not limited thereto. It is also preferable toemploy these compounds as a positive hole inhibition material.

In the emission layer according to the present invention, prior art hostcompounds may be employed in combinations of a plurality of types. Theuse of a plurality of host compounds enables regulation of migration ofelectrons to make organic EL elements more efficient. Preferred as theseprior art host compounds are those which exhibit positive holetransportability and electron transportability, minimize the variationof luminescent wavelength to a longer wavelength, and attain a high Tg(being a glass transition temperature).

Further, an emission host of this invention may be either a lowmolecular weight compound or a polymer compound having a repeating unit,in addition to a low molecular weight compound provided with apolymerizing group such as a vinyl group and an epoxy group (anevaporation polymerizing emission host).

An emission host is preferably a compound having a positive holetransporting ability and an electron transporting ability, as well aspreventing elongation of an emission wavelength and having a high Tg (aglass transition temperature).

As specific examples of an emission host, compounds described in thefollowing Documents are preferable: For example, JP-A Nos. 2001-257076,2002-308855, 2001-313179, 2002-319491, 2001-357977, 2002-334786,2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056,2002-334789, 2002-75645, 2002-338579, 2002-105445, 2002-343568,2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453,2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861,2002-280183, 2002-299060, 2002-302516, 2002-305083, 2002-305084 and2002-308837. Specific examples of an emission host are shown below;however, this invention is not limited thereto.

The emission layer may further incorporate, as a host compound, acompound which exhibits a maximum fluorescent wavelength. In such acase, luminescence is also generated from the other host compound,resulting in the maximum fluorescent wavelength in the form ofelectromagnetic luminescence as an organic EL element due to energytransfer from the other host compound and a phosphorescent compound tothe fluorescent compound. Preferred as such host compounds resulting inthe maximum fluorescent wavelength are those which attain a highfluorescent quantum yield. Herein, the fluorescent quantum yield ispreferably at least 10%, but is more preferably at least 30%. Specificexamples of host compounds resulting in the maximum fluorescentwavelength include coumarin based dyes, pyran based dyes, cyanine baseddyes, croconium based dyes, suqualium based dyes, oxobenzanthracenebased dyes, fluorescein based dyes, ROHDAMINE based dyes, pyrylium baseddyes, perylene based dyes, stilbene based dyes, and polythiophene baseddyes. The fluorescent quantum yield can be determined based on themethod described on page 362 of Bunko (Spectroscopy) II of aforesaidZikken Kagaku Koza (Lecture on Experimental Chemistry) 7, 4th Edition(published by Maruzen, 1992).

Next, a typical constitution of an organic EL element will be described.

<Constituent Layers of Organic EL Element>

Constituent layers of an organic EL element of this invention will nowbe explained.

Specific examples of a preferable layer constitution of an organic ELelement of this invention are shown below; however, this invention isnot limited thereto.

-   (i) anode/positive hole transport layer/emission layer/positive hole    inhibition layer/electron transport layer/cathode,-   (ii) anode/electron inhibition layer/emission layer/positive hole    inhibition layer/electron transport layer/cathode,-   (iii) anode/positive hole transport layer/electron inhibition    layer/emission layer/positive hole inhibition layer/electron    transport layer/cathode,-   (iv) anode/anode buffer layer/positive hole transport layer/electron    inhibition layer/emission layer/positive hole inhibition    layer/electron transport layer/cathode,-   (v) anode/positive hole transport layer/electron inhibition    layer/emission layer/positive hole inhibition layer/electron    transport layer/cathode buffer layer/cathode,-   (vi) anode/anode buffer layer/positive hole transport layer/electron    inhibition layer/emission layer/positive hole inhibition    layer/electron transport layer/cathode buffer layer/cathode,-   (vii) anode/anode buffer layer/positive hole transport    layer/electron inhibition layer/emission layer/positive hole    inhibition layer/electron transport layer/cathode buffer    layer/cathode.

<Inhibition Layer (Electron Inhibition Layer, Positive Hole InhibitionLayer)>

An inhibition layer (such as an electron inhibition layer, a positivehole inhibition layer) according to this invention will now beexplained.

In this invention, an organic EL element material of this invention ispreferably utilized in such as a positive hole inhibition layer and anelectron inhibition layer, and specifically preferably in a positivehole inhibition layer.

In the case of an organic EL element material of this invention beingcontained in a positive hole inhibition layer and an electron inhibitionlayer, a metal complex according to this invention, which is describedin any one of the above-described embodiments 1-7, may be contained in astate of 100 weight % as a layer constituent component of such as apositive hole inhibition layer and an electron inhibition layer, or maybe contained by being mixed with another organic compound (such ascompounds utilized in a constituent layer of an organic EL element ofthis invention).

The layer thickness of an inhibition layer according to this inventionis preferably 3-100 nm and more preferably 5-30 nm.

<Positive Hole Inhibition Layer>

A positive hole inhibition layer, in a broad meaning, is provided with afunction of electron transport layer, being comprised of a materialhaving a function of transporting an electron but a very small abilityof transporting a positive hole, and can improve the recombinationprobability of an electron and a positive hole by inhibiting a positivehole while transporting an electron.

As a positive hole inhibition layer, for example, a positive inhibitionlayer described in such as JP-A Nos. 11-204258 and 11-204359 and p. 273of “Organic EL Elements and Idustrialization Front Thereof (Nov. 30(1998), published by N. T. S Corp.)” is applicable to a positive holeinhibition (hole block) layer according to this invention. Further, aconstitution of an electron transport layer described later can beappropriately utilized as a positive hole inhibition layer according tothis invention.

It is preferable that the organic EL layer of the present inventionincorporates a positive hole layer, which incorporates derivativeshaving a ring structure, in which at least one carbon atom of thehydrocarbon ring constituting the above carboline derivative or thecarboline ring of the above carboline derivative is substituted with anitrogen atom.

<Electron Inhibition Layer>

On the other hand, an electron inhibition layer is, in a broad meaning,provided with a function of a positive hole transport layer, beingcomprised of a material having a function of transporting a positivehole but a very small ability of transporting an electron, and canimprove the recombination probability of an electron and a positive holeby inhibiting an electron while transporting a positive hole. Further, aconstitution of a positive hole transport layer described later can beappropriately utilized as an electron inhibition layer.

Further, in this invention, it is preferable to utilize an organic ELelement material of this invention described above in an adjacent layerneighboring to an emission layer, that is in a positive hole inhibitionlayer and an electron inhibition layer, and specifically preferably in apositive hole inhibition layer.

<Positive Hole Transport Layer>

A positive hole transport layer contains a material having a function oftransporting a positive hole, and in a broad meaning, a positive holeinjection layer and an electron inhibition layer are also included in apositive hole transport layer. A single layer of or plural layers of apositive hole transport layer may be provided.

A positive hole transport material is not specifically limited and canbe arbitrary selected from those such as generally utilized as a chargeinjection transporting material of a positive hole in a conventionalphotoconductive material and those which are well known in the art andutilized in a positive hole injection layer and a positive holetransport layer of an EL element.

A positive hole transport material is those having any one of a propertyto inject or transport a positive hole or a barrier property to anelectron, and may be either an organic substance or an inorganicsubstance. For example, listed are a triazole derivative, an oxadiazolederivative, an imidazole derivative, a polyallylalkane derivative, apyrazolone derivative, a phenylenediamine derivative, a allylaminederivative, an amino substituted chalcone derivative, an oxazolederivatives, a styrylanthracene derivative, a fluorenone derivative, ahydrazone derivative, a stilbene derivative, a silazane derivative, ananiline type copolymer, or conductive polymer oligomer and specificallypreferably such as thiophene oligomer.

As a positive hole transport material, those described above can beutilized, however, it is preferable to utilized a porphyrin compound, anaromatic tertiary amine compound and a styrylamine compound, andspecifically preferably an aromatic tertiary amine compound.

Typical examples of an aromatic tertiary amine compound and astyrylamine compound include N,N,N′,N′-tetraphenyl-4,4′-diaminophenyl;N,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine(TDP); 2,2-bis(4-di-p-tolylaminophenyl)propane;1,1-bis(4-di-p-tolylaminophenyl)cyclohexane;N,N,N′,N′-tetra-p-tolyl4,4′-diaminobiphenyl;1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane;bis(4-dimethylamino-2-metyl)phenylmethane;bis(4-di-p-tolylaminophenyl)phenylmethane;N,N′-diphenyl-N,N′-di(4-methoxyphenyl)-4,4′-diaminobiphenyl;N,N,N′,N′-tetraphenyl-4,4′-diaminophenylether;4,4′-bis(diphenylamino)quarterphenyl; N,N,N-tri(p-tolyl)amine;4-(di-p-tolylamino)-4′-[4-(di-p-triamino)styryl]stilbene;4-N,N-diphenylamino-(2-diphenylvinyl)benzene;3-methoxy-4′-N,N-diphenylaminostilbene; and N-phenylcarbazole, inaddition to those having two condensed aromatic rings in a moleculedescribed in U.S. Pat. No. 5,061,569, such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NDP), and4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (MDTDATA),in which three of triphenylamine units are bonded in a star burst form,described in JP-A 4-308688.

Polymer materials, in which these materials are introduced in a polymerchain or constitute the main chain of polymer, can be also utilized.Further, an inorganic compound such as a p type-Si and a p type-SiC canbe utilized as a positive hole injection material and a positive holetransport material

This positive hole transport layer can be prepared by forming a thinlayer made of the above-described positive hole transport materialaccording to a method well known in the art such as a vacuum evaporationmethod, a spin coating method, a cast method, an inkjet method and a LBmethod. The layer thickness of a positive hole transport layer is notspecifically limited, however, is generally 5-5,000 nm. This positivetransport layer may have a single layer structure comprised of one ornot less than two types of the above described materials.

<Electron Transport Layer>

An electron transfer layer is comprised of a material having a functionto transfer an electron, and an electron injection layer and a positivehole inhibition layer are included in an electron transfer layer in abroad meaning. A single layer or plural layers of an electron transferlayer may be provided.

Conventionally, as an electron transfer material utilized in a singlelayer of an electron transfer layer, and in an electron transfer layeradjacent to the cathode side against an emission layer in the case ofutilizing plural electron transfer layers, the following materials areknown.

Further, an electron transfer layer is provided with a function totransmit an electron injected from a cathode to an emission layer, andcompounds conventionally well known in the art can be utilized byarbitrarily selection as a material thereof.

Examples of a material utilized in this electron transfer layer(hereinafter, referred to as an electron transfer material) include suchas a nitro-substituted fluorene derivative, a diphenylquinonederivative, a thiopyradineoxide derivative, a heterocyclic tetracarbonicacid anhydride such as naphthaleneperylene, carbodiimide, afluorenylidenemethane derivative, anthraquinonedimethane and anthronederivatives, and an oxadiazole derivative. Further, a thiazolederivative in which an oxygen atom in the oxadiazole ring of theabove-described oxadiazole derivative is substituted by a sulfur atom,and a quinoxaline derivative having a quinoxaline ring which is known asan electron attracting group can be utilized as an electron transfermaterial.

Polymer materials, in which these materials are introduced in a polymerchain or these materials form the main chain of polymer, can be alsoutilized.

Further, a metal complex of a 8-quinolinol derivative such astris(8-quinolinol)aluminum (Alq),tris(5,7-dichloro-8-quinolinol)aluminum,tris(5,7-dibromo-8-quinolinol)aluminum,tris(2-methyl-8-quinolinol)aluminum, tris(5-methyl-8-quinolinol)aluminumand bis(8-quinolinol)zinc (Znq); and metal complexes in which a centralmetal of the aforesaid metal complexes is substituted by In, Mg, Cu, Ca,Sn, Ga or Pb, can be also utilized as an electron transfer material.Further, metal-free or metal phthalocyanine, or those the terminal ofwhich is substituted by an alkyl group and a sulfonic acid group, can bepreferably utilized as an electron transfer material. Further,distyrylpyrazine derivative, which has been exemplified as a material ofan emission layer, can be also utilized as an electron transfermaterial, and, similarly to the case of a positive hole injection layerand a positive hole transfer layer, an inorganic semiconductor such asan n-type-Si and an n-type-SiC can be also utilized as an electrontransfer material.

This electron transport layer can be prepared by forming a thin layermade of the above-described electron transport material according to amethod well known in the art such as a vacuum evaporation method, a spincoating method, a cast method, an inkjet method and a LB method. Thelayer thickness of an electron transport layer is not specificallylimited; however, is generally 5-5,000 nm. This electron transport layermay have a single layer structure comprised of one or not less than twotypes of the above described materials.

Next, an injection layer which is known as a constituent layer of anorganic EL element of this invention will be explained.

<Injection Layer>: Electron Injection Layer, Positive Hole InjectionLayer

An injection layer is appropriately provided and includes an electroninjection layer and a positive hole injection layer, which may bearranged between an anode and an emission layer or a positive transferlayer, and between a cathode and an emission layer or an electrontransfer layer, as described above.

An injection layer is a layer which is arranged between an electrode andan organic layer to decrease an operating voltage and to improve anemission luminance, which is detailed in volume 2, chapter 2 (pp.123-166) of “Organic EL Elements and Industrialization Front thereof(Nov. 30th 1998, published by N. T. S Corp.)”, and includes a positivehole injection layer (an anode buffer layer) and an electron injectionlayer (a cathode buffer layer).

An anode buffer layer (a positive hole injection layer) is also detailedin such as JP-A 9-45479, 9-260062 and 8-288069, and specific examplesinclude such as a phthalocyanine buffer layer comprising such as copperphthalocyanine, an oxide buffer layer comprising such as vanadium oxide,an amorphous carbon buffer layer, and a polymer buffer layer employingconductive polymer such as polythiophene.

A cathode buffer layer (an electron injection layer) is also detailed insuch as JP-A 6-325871, 9-17574 and 10-74586, and specific examplesinclude a metal buffer layer comprising such as strontium and aluminum,an alkali metal compound buffer layer comprising such as lithiumfluoride, an alkali earth metal compound buffer layer comprising such asmagnesium fluoride, and an oxide buffer layer comprising such asaluminum oxide.

The above-described buffer layer (injection layer) is preferably a verythin layer, and the layer thickness is preferably in a range of 0.1-100nm although it depends on a raw material.

This injection layer can be prepared by forming a thin layer made of theabove-described material according to a method well known in the artsuch as a vacuum evaporation method, a spin coating method, a castmethod, an inkjet method and a LB method. The layer thickness of aninjection layer is not specifically limited; however, is generally5-5,000 nm. This injection layer may have a single layer structurecomprised of one or not less than two types of the above describedmaterials.

<Anode>

As an anode according to an organic EL element of this invention, thosecomprising metal, alloy, a conductive compound, which is provided with alarge work function (not less than 4 eV), and a mixture thereof as anelectrode substance are preferably utilized. Specific examples of suchan electrode substance include a conductive transparent material such asmetal like Au, CuI, indium tin oxide (ITO), SnO₂ and ZnO. Further, amaterial such as IDIXO (In₂O₃—ZnO), which can prepare an amorphous andtransparent electrode, may be also utilized. As for an anode, theseelectrode substances may be made into a thin layer by a method such asevaporation or spattering and a pattern of a desired form may be formedby means of photolithography, or in the case of requirement of patternprecision is not so severe (not less than 100 μm), a pattern may beformed through a mask of a desired form at the time of evaporation orspattering of the above-described substance. When emission is taken outof this anode, the transmittance is preferably set to not less than 10%and the sheet resistance as an anode is preferably not more than a fewhundreds Ω/□. Further, although the layer thickness depends on amaterial, it is generally selected in a range of 10-1,000 nm andpreferably of 10-200 nm.

<Cathode>

On the other hand, as a cathode according to this invention, metal,alloy, a conductive compound and a mixture thereof, which have a smallwork function (not more than 4 eV), are utilized as an electrodesubstance. Specific examples of such an electrode substance includessuch as sodium, sodium-potassium alloy, magnesium, lithium, amagnesium/copper mixture, a magnesium/silver mixture, amagnesium/aluminum mixture, a magnesium/indium mixture, analuminum/aluminum oxide (Al₂O₃) mixture, indium, a lithium/aluminummixture and rare earth metal. Among them, with respect to an electroninjection property and durability against such as oxidation, preferableare a mixture of electron injecting metal with the second metal which isstable metal having a work function larger than electron injectingmetal, such as a magnesium/silver mixture, a magnesium/aluminum mixture,a magnesium/indium mixture, an aluminum/aluminum oxide (Al₂O₃) mixtureand a lithium/aluminum mixture, and aluminum. As for a cathode, theseelectrode substances may be made into a thin layer by a method such asevaporation or spattering. Further, the sheet resistance as a cathode ispreferably not more than a few hundreds Ω/□ and the layer thickness isgenerally selected in a range of 10-1,000 nm and preferably of 10-200nm. Herein, to transmit emission, either one of an anode or a cathode ofan organic EL element is preferably transparent or translucent toimprove the mission luminance.

<Substrate (Also Referred to as Base Plate, Base Material or Support)>

A substrate according to an organic EL element of this invention is notspecifically limited with respect to types of such as glass and plasticsprovided being transparent, however, a substrate preferably utilizedincludes such as glass, quartz and transparent resin film. Aspecifically preferable substrate is resin film capable of providing anorganic EL element with a flexible property.

Resin film includes such as film comprised of polyethylene terephthalate(PET), polyethylene naphthalate (PEN), polyether sulphone (PES),polyether imide, polyether etherketone, polyphenylene sulfide,polyallylate, polyimide, polycarbonate (PC) and cellulose acetatepropionate (CAP).

On the surface of resin film, an inorganic or organic cover layer or ahybrid cover layer comprising the both may be formed, and the film ispreferably provided with a high barrier ability having a vaportransmittance of not more than 0.01 g/m²·day·at a temperature of 25±0.5°C., relative humidity (90±2)% RH, measured based on JIS K 7129-1992.

The taking out efficiency of emission of an organic EL element of thisinvention at room temperature is preferably not less than 1% and morepreferably not less than 2%. Herein, taking out quantum efficiency(%)=photon number emitted out of organic EL element/electron numberflown into organic EL element×100.

Further, a hue improving filter such as a color filter may be utilizedin combination.

In the case of an illumination application, roughening processed film(such as anti-glare film) can be also utilized in combination todecrease emission unevenness.

In the case of an application as a multi-color display device, thedisplay is comprised of at least two types of organic EL elements havingdifferent emission maximum wavelengths, and a preferable example toprepare an organic EL element will now be explained.

<Preparation Method of Organic EL Element>

As an example of a preparation method of an organic EL element of thisinvention, a preparation method of an organic EL element, comprisinganode/positive hole injection layer/positive hole transportlayer/emission layer/positive hole inhibition layer/electron transportlayer/cathode buffer layer/cathode, will be explained.

First, on an appropriate substrate, a thin layer comprising a desiredelectrode substance such as an anode electrode substance is formed bymeans of evaporation or spattering so as to make a layer thickness ofnot more than 1 μm and preferably of 10-200 nm, whereby an anode isprepared. Next, on this layer, thin layers containing organic substancesof such as a positive hole injection layer, a positive hole transportlayer, an emission layer, a positive hole inhibition layer and anelectron transport layer are formed.

A thin layer forming method of these layers containing the organicsubstances includes such as a spin coat method, a cast method, an inkjetmethod, an evaporation method and a printing method as described before,however, a vacuum evaporation method or a spin coat method isspecifically preferable with respect to easy preparation of ahomogeneous layer and bare generation of pinholes. Further, a differentlayer forming method depending on each layer may be applied. In the caseof employing an evaporation method in layer formation, the evaporationcondition depends on such as the type of a utilized compound, however,is generally appropriately selected in a range of 50-450° C. as a boatheating temperature, 10⁻⁶-10⁻² Pa as a vacuum degree, 0.01-50 nm/sec asa deposition rate, −50-300° C. as a substrate temperature and 1 nm-5 μmas a layer thickness.

After formation of these layers, a thin layer comprising a cathodeelectrode substance is formed thereon by means of such as evaporation orspattering so as to make a layer thickness in a range of 50-200 nm toprovide a cathode, whereby a desired organic EL element can be prepared.This preparation of an organic EL element is preferably carried out withone time evacuation to prepare all through from a positive holeinjection layer to a cathode, however, different layer forming methodmay be also applied by taking out the element on the way. At that time,it is preferable to take consideration such as to perform the operationunder a dry inert gas environment.

<Display Device>

A display device of this invention will now be explained. The displaydevice of this invention includes the above-described organic ELelement.

A display device of this invention may be either monochromatic ormulti-colored. Here explained will be a multicolor display device. Inthe case of a multicolor display device, a shadow mask is provided onlyat the time of emission layer formation, and layers can be formed allover the surface by such as an evaporation method, a cast method, a spincoat method, an inkjet method and a printing method.

When patterning is performed only with an emission layer, the method isnot specifically limited; however, preferable are an evaporation method,an inkjet method and a printing method. And patterning employing ashadow mask is preferred in the case of an evaporation method.

Further, reversing the preparation order, it is also possible to preparelayers in the order of a cathode, an electron transport layer, apositive hole inhibition layer, an emission layer, a positive holetransport layer and an anode.

When a direct current voltage is applied on the multicolor displaydevice thus prepared, emission can be observed by application of avoltage of approximately 2-40 V setting an anode to + polarity and acathode to − polarity. Further, no current flows and no emissiongenerate at all even when a voltage is applied with a reversed polarity.Further, in the case of alternate current voltage being applied,emission generates only in a state of an anode being + and a cathodebeing −. Herein, the wave shape of alternate current may be arbitrary.

A multicolor display device can be utilized as a display device, adisplay and various types of emission light sources. In a display deviceand a display, full-colored display is possible by employing three typesof organic EL elements providing blue, red and green emissions.

A display device and a display include a TV, a personal computer, amobile instrument, an AV instrument, a character broadcast display andan information display in a car. Particularly, the display device andthe display may be also utilized as a display to playback still imagesand moving images, and may adopt either a simple matrix (a passivematrix) mode or an active matrix mode when being utilized as a displaydevice for moving image playback.

An illumination light source includes a home use illumination, a carroom illumination, a backlight of a watch or a liquid crystal, a paneladvertisement, a signal, a light source of an optical memory medium, alight source for an electrophotographic copier, a light source for anoptical telecommunication processor and a light source for aphoto-sensor, however, is not limited thereto.

<Illumination Device>

An illumination device (or a lighting device) of this invention will nowbe explained. The illumination device of this invention includes theabove-described organic EL element.

An organic EL element of this invention can be utilized as an organic ELelement provided with a resonator structure, and a utilization purposeof such an organic EL element provided with a resonator structureincludes such as a light source for an optical memory medium, a lightsource for an electrophotographic copier, a light source for a opticaltelecommunication processor and a light source for a photo-sensor,however, is not limited thereto. Further, the organic EL element may beutilized for the above-described applications by being made to performlaser emission.

Further, an organic EL element of this invention may be utilized as onetype of a lamp like an illumination and an exposure light, and may bealso utilized as a display device of a projector of an image projectingtype and a display device (a display) of a type to directly view stillimages and moving images. An operating mode in the case of beingutilized as a display device for playback of moving images may be eithera simple matrix (a passive matrix) mode or an active matrix mode. Inaddition, a full-color display device can be prepared by utilizing atleast two types of organic EL elements of this invention which emitdifferent emitting colors.

In the following, one example of a display device provided with anorganic EL element of this invention will be explained.

FIG. 1 is a schematic drawing to show an example of a display deviceconstituted of an organic EL element. It is a schematic drawing of adisplay, which displays image information by emission of an organic ELelement, such as a mobile phone.

Display 1 is constituted of such as display section A having pluralnumber of pixels and control section B which performs image scanning ofdisplay section A based on image information.

Control section B, which is electrically connected to display section A,sends a scanning signal and an image data signal to plural number ofpixels based on image information from the outside and pixels of eachscanning line successively emit depending on the image data signal by ascanning signal to perform image scanning, whereby image information isdisplayed on display section A.

FIG. 2 is a schematic drawing of display section A.

Display section A is provided with such as a wiring part, which containsplural scanning lines 5 and data lines 6, and plural pixels 3 on asubstrate. Primary part materials of display section A will be explainedin the following.

In the drawing, shown is the case that light emitted by pixel 3 is takenout along the white allow (downward).

Scanning lines 5 and plural data lines 6 in a wiring part each arecomprised of a conductive material, and scanning lines 5 and data lines6 are perpendicular in a grid form and are connected to pixels 3 at theright-angled crossing points (details are not shown in the drawing).

Pixel 3 receives an image data from data line 6 when a scanning signalis applied from scanning line 5 and emits according to the receivedimage data. Full-color display device is possible by appropriatelyarranging pixels having an emission color in a red region, pixels in agreen region and pixels in a blue region, side by side on the samesubstrate.

Next an emission process of a pixel will be explained.

FIG. 3 is a schematic drawing of a pixel.

A pixel is equipped with such as organic EL element 10, switchingtransistor 11, operating transistor 12 and condenser 13. Red, green andblue emitting organic EL elements are utilized as organic EL element 10for plural pixels, and full-color display device is possible byarranging these side by side on the same substrate.

In FIG. 3, an image data signal is applied on the drain of switchingtransistor 11 via data line 6 from control section B. Then, when ascanning signal is applied on the gate of switching transistor 11 viascanning line 5 from control section B, operation of switchingtransistor is on to transmit the image data signal applied on the drainto the gates of condenser 13 and operating transistor 12.

Operating transistor 12 is on, simultaneously with condenser 13 beingcharged depending on the potential of an image data signal, bytransmission of an image data signal. In operating transistor 12, thedrain is connected to electric source line 7 and the source is connectedto the electrode of organic EL element 10, and an electric current issupplied from electric source line 7 to organic EL element 10 dependingon the potential of an image data applied on the gate.

When a scanning signal is transferred to next scanning line 5 bysuccessive scanning of control section B, operation of switchingtransistor 11 is off. However, since condenser 13 keeps the chargedpotential of an image data signal even when operation of switchingtransistor 11 is off, operation of operating transistor 12 is kept on tocontinue emission of organic EL element 10 until the next scanningsignal is applied. When the next scanning signal is applied bysuccessive scanning, operating transistor 12 operates depending on thepotential of an image data signal synchronized to the scanning signaland organic EL element 10 emits.

That is, emission of each organic EL element 10 of plural pixels 3 isperformed by providing switching transistor 11 and operating transistor12 against each organic EL element 10 of plural pixels 3. Such anemission method is called as an active matrix mode.

Herein, emission of organic EL element 10 may be either emission ofplural gradations based on a multiple-valued image data signal havingplural number of gradation potentials or on and off of a predeterminedemission quantity based on a binary image data signal. Further,potential hold of condenser 13 may be either continuously maintaineduntil the next scanning signal application or discharged immediatelybefore the next scanning signal application.

In this invention, emission operation is not necessarily limited to theabove-described active matrix mode but may be a passive matrix mode inwhich organic EL element is emitted based on a data signal only when ascanning signal is scanned.

FIG. 4 is a schematic drawing of a display device based on a passivematrix mode. In FIG. 4, plural number of scanning lines 5 and pluralnumber of image data lines 6 are arranged grid-wise, opposing to eachother and sandwiching pixels 3.

When a scanning signal of scanning line 5 is applied by successivescanning, pixel 3 connected to scanning line 5 applied with said signalemits depending on an image data signal.

Since pixel 3 is provided with no active element in a passive matrixmode, decrease of manufacturing cost is possible.

An organic EL element material of this invention can be also applied toan organic EL element to generate emission of practically white color asan illumination device. Plural emission colors are simultaneouslyemitted by plural number of emission materials to obtain white light bymixing colors. A combination of plural emission colors may be either theone, in which three emission maximum wavelengths of three primary colorsof blue, green and red are contained, or the other, in which twoemission maximum wavelengths, utilizing a relationship of complimentarycolors such as blue and yellow, or blue and orange, are contained.

Further, a combination of emission materials to obtain plural number ofemission colors may be either a combination comprising plural number ofmaterials which emit phosphoresce or fluorescence, or a combination of amaterial which emits phosphoresce or fluorescence and a dye materialwhich emits by light from an emission material as exiting light,however, in a white organic electroluminescent element according to thisinvention, it is enough only to mix plural emission dopants incombination. A mask is provided only at the time of forming such as anemission layer, a positive hole transport layer or an electron transportlayer, to only simply arrange the plural emission dopants such as byseparately painting through the mask, while other layers are commonlyutilized to require no patterning such as a mask. Therefore, such as anelectrode can be formed all over the plane by such as an evaporationmethod, a cast method, a spin coat method, an inkjet method and aprinting method, resulting in improvement of productivity. According tothis method, different from a white organic EL device in which pluralcolors of emission elements are arranged parallel in an alley form, anelement itself is white emitting.

An emission material utilized in an emission layer is not specificallylimited, and in the case of a backlight of a liquid crystal displayelement, any combination by arbitrary selection among platinum complexesaccording to this invention or emission materials well known in the artcan be utilized so as to be fitted to the wavelength range correspondingto CF (color filter) characteristics, whereby white emission can beobtained.

In this manner, a white emitting organic EL element of this invention isusefully utilized as one type of a lamp such as a home use illumination,a car room illumination or an exposure light source as various emissionlight sources or illumination devices, in addition to the aforesaiddisplay device and a display, and is further usefully applied for adisplay as such as a backlight of a liquid crystal display.

In addition to these, listed is a wide range of applications such as abacklight of a watch, an advertising board, a signal, a light source ofan optical memory medium, a light source of an electrophotographiccopier, a light source of an optical telecommunication processor and alight source of an optical sensor, and further general home use electricinstruments which require a display device.

EXAMPLES

In the following, this invention will be explained with reference toexamples, however, is not limited thereto.

Example 1 <Preparation of Organic EL Element 1-1>

After a substrate, in which ITO had been deposited at 150 nm on a glassplate as an anode (NA-45 produced by NH Techno Glass Co. Ltd.) wassubjected to patterning, the transparent support substrate was washedwith isopropyl alcohol by use of ultrasonic waves, followed by beingdried with a dry nitrogen gas, and was subjected to UV ozone washing for5 minutes. This transparent support substrate was fixed on a substrateholder of a vacuum evaporation system available on the market, and onthe other hand, each of five resistance heating boats made of tantalumwas charged with α-NPD, H4, Ir-12, BCP and Alq₃, respectively, which wasattached in the vacuum evaporation system (in the first vacuum chamber).

Further, a resistance heating boat made of tantalum was charged withlithium fluoride and a resistance heating boat made of tungsten wascharged with aluminum, respectively, and these boats were attached inthe second chamber of the vacuum evaporation system.

First, after the first vacuum chamber was evacuated down to 4×10⁻⁴ Pa,the aforesaid heating boat charged with α-NPD was heated with anelectric current to deposit α-NPD on a support substrate at a depositionrate of 0.1-0.2 nm/sec so as to make a layer thickness of 20 nm, wherebya positive hole injection/transport layer was formed.

Further, the aforesaid heating boat charged with H4 and the boat chargedwith Ir-12 were independently supplied with an electric current todeposit H4 as an emission host and Ir-12 as an emission dopant so as tomake a layer thickness of 30 nm while adjusting the deposition ratesthereof to 100:6, whereby an emission layer was formed.

Next, the aforesaid heating boat charged with BCP was heated with anelectric current to provide a positive hole inhibition layer having alayer thickness of 10 nm at a deposition rate of 0.1-0.2 nm/sec.Further, the aforesaid heating boat charged with Alq₃ was heated with anelectric current to provide an electron transport layer having a layerthickness of 20 nm at a deposition rate of 0.1-0.2 nm/sec.

Next, after an element having been deposited with up to an electroninjection layer as described before was transferred into the secondvacuum chamber while keeping vacuum, a mask, which was made of stainlesssteel and had rectangular holes, was arranged on the electron injectionlayer by means of remote control from outside of the system.

After the second vacuum chamber was evacuated down to 2×10⁻⁴ Pa, a boatcharged with lithium fluoride was supplied with an electric current toprovide a cathode buffer layer having a layer thickness of 0.5 nm at adeposition rate of 0.01-0.02 nm/sec, and then a boat charged withaluminum was supplied with an electric current to provide a cathodehaving a layer thickness of 150 nm at a deposition rate of 1-2 nm/sec toobtain Organic EL Element 1-1.

<Preparation of Organic EL Elements 1-2-1-21>

Organic EL Elements 1-2-1-21 each were prepared in a similar manner topreparation of organic EL element 1-1 described above, except that anemission dopant was changed as shown in table 2.

<<Evaluation of Organic EL Elements>>

When resulting Organic EL Elements 1-1-1-21 were evaluated, after theirpreparation, the non-luminescent side was covered with a glass case, anda 300 μm thick glass substrate was employed as a sealing substrate.Further, an epoxy based radiation curable type adhesive (LAXTRACKC0629B, produced by TOAGOSEI Co., Ltd.) was applied to the periphery asa sealing agent. The resulting substrate was overlapped onto the aboveanode to come into close contact with the above transparent supportingsubstrate. Subsequently, UV radiation was exposed to the glass substrateside to result in curing and sealing. Thus, the lighting device as shownin FIGS. 5 and 6 was formed and evaluation was then carried out.

FIG. 5 is a schematic view of a lighting device. Organic EL element 101is covered with glass cover 102 (sealing operation employing the glasscover was carried out in a globe box (under an atmosphere of high puritynitrogen gas at a purity of at least 99.999%) without contact withatmospheric air). FIG. 6 is a sectional view of the lighting device, inwhich numeral 105 represents a cathode, 106 represents an organic ELlayer, and 107 represents a glass substrate fitted with a transparentelectrode. Further, nitrogen gas 108 is fed into glass cover 102, anddesiccant 109 is provided.

<Quantum Efficiency of Taking Out>

Each of organic EL elements was lighted under a constant currentcondition of 2.5 mA/cm² at room temperature (approximately 23-25° C.),and an emission luminance (L) [cd/m²] immediately after turning on wasmeasured, whereby a quantum efficiency of taking out (η) was calculated.Herein, CS-1000 (produced by Konica Minolta Sensing Inc.) was utilizedfor measurement of emission luminance. Further, each of the quantumefficiency of taking out was expressed as a relative value when that oforganic EL element 1-1 was set to 100.

<Emission Life>

Each of organic EL elements was continuously lighted under a constantcurrent condition of 2.5 mA/cm² at room temperature (approximately23-25° C.), and time to reach a half of the initial luminance (τ½) wasmeasured. Further, each emission life was expressed as a relative valuewhen that of organic EL element 1-1 was set to 100.

<Luminescent Color>

Each of organic EL elements was continuously lighted under a constantcurrent condition of 2.5 mA/cm² at room temperature (approximately23-25° C.). The luminescent color was visibly observed and evaluated.

The obtained results are shown in table 2.

TABLE 2 Organic Taking- EL Emis- out Lumines- Lumines- Element sionEmission Quantum cent cent Re- No. host dopant Yield Lifetime Colormarks 1-1 H4 Ir-12 100 100 Bluish Comp. green 1–2 H4 Compar- 75 95yellowish Comp. ative 1 green 1–3 H4 Compar- 109 113 yellow Comp. ative2 1–4 H4 Compar- 112 40 pale Comp. ative 3 bluish white 1–5 H4  (3) 128325 pure blue Inv. 1–6 H4 (17) 133 488 pure blue Inv. 1–7 H4 (23) 129342 pure blue Inv. 1–8 H4 (34) 134 470 pure blue Inv. 1–9 H4 (42) 129445 pure blue Inv. 1–10 H4 (54) 135 538 blue Inv. 1–11 H6 (68) 141 501blue Inv. 1–12 H6 (83) 139 529 pure blue Inv. 1–13 H6 (95) 135 520 pureblue Inv. 1–14 H6 (97) 142 649 bluish Inv. green 1–15 H6 (123)  145 588pure blue Inv. 1–16 H6 (133)  141 613 blue Inv. 1–18 H30 (154)  149 688blue Inv. 1–19 H30 (176)  143 632 blue Inv. 1–20 H30  (3) 135 362 blueInv. 1–21 H30 (97) 150 678 bluish Inv. green Comp.: Comparative Example,Inv.: Present Invention

Based on Table 2, it is clear that the organic EL elements prepared viathe metal complexes according to the present invention attain highluminescent efficiency and extended luminescent lifetime, compared tothe EL element of the Comparative Examples. In addition, compared to theorganic EL elements of the Comparative Examples, it was found that thepurity of blue color is higher, resulting in a more useful blueluminescent element. Further, it was noticed that by simultaneouslyemploying, in the emission layer, a derivative having the ring structurein which at least one carbon atom of the hydrocarbon ring constitutingthe carboline derivative or the carboline ring of the carbolinederivative was substituted with a nitrogen atom, targeted effects of thepresent invention were further enhanced.

Example 2 <Preparation of Organic EL Element 2-1>

After a substrate, in which ITO had been deposited at 150 nm on a glassplate as an anode (NA-45 produced by NH Techno Glass Co. Ltd.) wassubjected to patterning, the transparent support substrate was washedwith isopropyl alcohol by use of ultrasonic waves, followed by beingdried with a dry nitrogen gas, and was subjected to UV ozone washing for5 minutes.

This transparent support substrate was fixed on a substrate holder of avacuum evaporation system available on the market, and on the otherhand, each of five resistance heating boats made of tantalum was chargedwith A-NPD, H2, Ir-13, BCP and Alq₃, respectively, which was attached inthe vacuum evaporation system (in the first vacuum chamber).

Further, a resistance heating boat made of tantalum was charged withlithium fluoride and a resistance heating boat made of tungsten wascharged with aluminum, respectively, and these boats were attached inthe second chamber of the vacuum evaporation system.

First, after the first vacuum chamber was evacuated down to 4×10⁻⁴ Pa,the aforesaid heating boat charged with α-NPD was heated with anelectric current to deposit α-NPD on a support substrate at a depositionrate of 0.1-0.2 nm/sec so as to make a layer thickness of 20 nm, wherebya positive hole injection/transport layer was formed.

Further, the aforesaid heating boat charged with H2 and the boat chargedwith Ir-13 were independently supplied with an electric current todeposit H2 as an emission host and Ir-13 as an emission dopant so as tomake a layer thickness of 30 nm while adjusting the deposition ratesthereof to 100:6, whereby an emission layer was formed.

Next, the aforesaid heating boat charged with BCP was heated with anelectric current to provide a positive hole inhibition layer having alayer thickness of 10 nm at a deposition rate of 0.1-0.2 nm/sec.Further, the aforesaid heating boat charged with Alq₃ was heated with anelectric current to provide an electron transport layer having a layerthickness of 20 nm at a deposition rate of 0.1-0.2 nm/sec.

Next, after an element having been deposited with up to an electroninjection layer as described before was transferred into the secondvacuum chamber while keeping vacuum, a mask, which was made of stainlesssteel and had rectangular holes, was arranged on the electron injectionlayer by means of remote control from outside of the system.

After the second vacuum chamber was evacuated down to 2×10⁻⁴ Pa, a boatcharged with lithium fluoride was supplied with an electric current toprovide a cathode buffer layer having a layer thickness of 0.5 nm at adeposition rate of 0.01-0.02 nm/sec, and then a boat charged withaluminum was supplied with an electric current to provide a cathodehaving a layer thickness of 150 nm at a deposition rate of 1-2 nm/sec toobtain Organic EL Element 2-1.

<Preparation of Organic EL Elements 2-2-2-31>

Organic EL Elements 2-2-2-31 each were prepared in a similar manner topreparation of organic EL element 2-1 described above, except that anemission dopant was changed as shown in table 3.

<<Evaluation of Organic EL elements>>

When resulting Organic EL Elements 2-1-2-31 were evaluated, after theirpreparation, the non-luminescent side was covered with a glass case, anda 300 μm thick glass substrate was employed as a sealing substrate.Further, an epoxy based radiation curable type adhesive (LAXTRACKC0629B, produced by TOAGOSEI Co., Ltd.) was applied to the periphery asa sealing agent. The resulting substrate was overlapped onto the aboveanode to come into close contact with the above transparent supportingsubstrate. Subsequently, UV radiation was exposed to the glass substrateside to result in curing and sealing. Thus, the lighting device as shownin FIGS. 5 and 6 was formed and evaluation was then carried out.

Taking-out quantum efficiency, luminescent lifetime, and luminescentcolor were evaluated in the same manner as for Example 1. The taking-outquantum efficiency and the luminescent lifetime were expressed byrelative values when each value of Organic EL Element 2-1 was 100. Table3 shows the results.

TABLE 3 Organic Taking- EL out Element Emission Emission QuantumLuminescent Luminescent No. host dopant *1 Yield Lifetime Color Remarks2-1 H2 Ir-13 BCP 100 100 yellowish Comp. green 2-2 H2 Comparative 1 BCP83 95 yellowish Comp. green 2-3 H2 Comparative 4 BCP 110 65 blue Comp.2-4 H2 Comparative 5 BCP 73 70 blue Comp. 2-5 H2 Comparative 6 BCP 90 69blue Comp. 2-6 H2 Comparative 7 BCP 94 100 bluish Comp. green 2-7 H2Comparative 8 BCP 108 94 yellow Comp. 2-8 H2 Comparative 9 BCP 125 889yellow Comp. 2-9 H2 (7) BCP 135 360 pure blue Inv. 2-10 H2 (27) BCP 140372 pure blue Inv. 2-11 H2 (38) BCP 142 368 pure blue Inv. 2-12 H4 (56)BCP 151 582 blue Inv. 2-13 H4 (77) BCP 153 603 blue Inv. 2-14 H4 (97)BCP 156 707 bluish Inv. green 2-15 H4 (106) BCP 149 668 blue Inv. 2-16H6 (113) BCP 154 692 blue Inv. 2-17 H6 (119) BCP 148 671 blue Inv. 2-18H6 (139) BCP 159 721 blue Inv. 2-19 H6 (146) BCP 157 764 pure blue Inv.2-20 H10 (150) BCP 155 738 pure blue Inv. 2-21 H10 (154) BCP 158 756blue Inv. 2-22 H10 (159) BCP 156 744 pure blue Inv. 2-23 H10 (161) BCP152 715 pure blue Inv. 2-24 H2 (7) H5 141 399 pure blue Inv. 2-25 H4(56) H5 156 615 blue Inv. 2-26 H4 (97) H5 161 738 bluish Inv. green 2-27H6 (119) H5 154 698 blue Inv. 2-28 H6 (146) H5 164 822 pure blue Inv.2-29 H10 (154) H26 166 798 blue Inv. 2-30 H10 (159) H26 163 801 pureblue Inv. 2-31 H10 (161) H26 159 745 pure blue Inv. Comp.: ComparativeExample, Inv.: Present Invention *1: Positive Hole Blocking Material

Based on Table 3, it is apparent that the organic EL elements preparedvia the metal complexes according to the present invention attained highluminescent efficiency and extended luminescent lifetime, compared tothe EL element of Comparative Examples. In addition, compared to theorganic EL elements resulting in long wavelength by employingComparative 9, it is clear that when the organic EL element materials ofthe present invention are employed, satisfactory effects to shorten thewavelength were realized.

Further, it was noticed that by simultaneously employing, in theemission layer, a derivative having the ring structure in which at leastone carbon atom of the hydrocarbon ring constituting the carbolinederivative or the carboline ring of the carboline derivative wassubstituted with a nitrogen atom, targeted effects of the presentinvention were further enhanced.

Example 3

A cathode (at a thickness of 200 nm) composed of an indium tin oxide(ITO at an indium/tin=95/5 mol ratio) was formed on a 25 mm×25 mm×0.5 mmglass substrate under application of a direct electric current,employing a sputtering method. The surface resistance of the resultingcathode was 10Ω/□. The above surface was coated with a dichloroethanesolution in which polyvinylcarbazole (being a positive hole transportingbinder polymer)/Ir-13 (being a blue fluorescent ortho metalcomplex)/2-(4-biphenylyl-5(4-t-butylphenyl)-1,3,4-oxazole (being anelectron transport material)=200/2/50 mole ratio were dissolved,employing a spin coater, whereby a 100 nm emission layer was prepared.On the resulting organic compound layer, a mask (being a mask resultingin a luminescent area of 5 mm×5 mm), which was subjected to patterning,was arranged and an anode was arranged in such a manner that in a vacuumevaporation device, 0.5 mm lithium fluoride was evaporated as an anodebuffer layer and 150 nm aluminum as a cathode was evaporated, wherebyBlue Luminescent Organic EL Element 3-1 was prepared.

<<Evaluation of Organic EL Elements>>

Organic EL Elements 3-2-3-11 were prepared in the same manner as OrganicEL Element 3-1, except that the emission dopant was changed as describedin Table 4.

When resulting Organic EL Elements 3-1-3-11 were evaluated, after theirpreparation, the non-luminescent side was covered with a glass case, anda 300 μm thick glass substrate was employed as a sealing substrate.Further, an epoxy based radiation curable type adhesive (LAXTRACKC0629B, produced by TOAGOSEI Co., Ltd.) was applied to the periphery asa sealing agent. The resulting substrate was overlapped onto the aboveanode to come into close contact with the above transparent supportingsubstrate. Subsequently, UV radiation was exposed to the glass substrateside to result in curing and sealing. Thus, the lighting device as shownin FIGS. 5 and 6 was formed and evaluation was then carried out.

Subsequently, luminance and luminescent efficiency were determined asdescribed below.

(Luminance and Luminescent Efficiency)

By employing SOURCE MAJOR UNIT Type 2400, produced by Toyo TechnicaInc., DC voltage was applied to an organic EL element to result inluminescence. Luminance (cd/m²) in the case in which 10 V DC voltage wasapplied, was determined and luminescent efficiency (lm/W). In the casein which an electric current of 2.5 mA/cm² was run, was also determined.Table 4 shows the results.

TABLE 4 Organic EL Luminescent Element Emission Luminance Efficiency No.dopant (cd/m²) (lm/W) Remarks 3-1 Ir-13 100 100 Comparative Example 3-2(7) 132 134 Present Invention 3-3 (39) 139 141 Present Invention 3-4(57) 142 142 Present Invention 3-5 (68) 140 141 Present Invention 3-6(95) 138 140 Present Invention 3-7 (97) 144 147 Present Invention 3-8(116) 146 150 Present Invention 3-9 (146) 153 156 Present Invention 3-10 (154) 155 157 Present Invention  3-11 (169) 154 155 PresentInvention

Based on Table 4, it is evident that the organic EL elements prepared byemploying the metal complexes according to the present inventionattained high luminescent efficiency and high luminance, compared to theEL element of the Comparative Example.

Example 4 <Preparation of Full-color Display Device> (Preparation ofBlue Emission Element)

Organic EL Element 1-18 of example 1 was utilized as a blue emissionelement.

(Preparation of Green Emission Element)

A green emission element was prepared by substituting Ir-13 used inOrganic EL element 2-1 of Example 2 with Ir-1.

(Preparation of Red Emission Element)

A red emission element was prepared by substituting Ir-13 used inOrganic EL element 2-1 of Example 2 with Ir-9.

Each of red, green and blue organic EL elements prepared above wasarranged parallel on the same substrate to prepare an active matrix modefull-color having a form as described in FIG. 1, and only displaysection A of said display device is schematically shown in FIG. 2. Thatis, a wiring section containing plural lines of scanning line 5 and dataline 6, and plural pixels 3 (such as a pixel having an emission color ofa red region, a pixel of a green region and a pixel of a blue region)arranged parallel are provided on the same substrate, and scanning lines5 and data lines 6 in a wiring section, which are comprised of aconductive material, respectively, cross each other at a right angle ina grid form to be connected to pixels 3 at the right-angled crossingpoints (details being not shown in the drawing). The aforesaid pluralpixels 3 each are operated in an active matrix mode, in which an organicEL element, a switching transistor and an operating transistor areprovided corresponding to each emission color, and receive an image datasignal from data line 6 when a scanning signal is applied from scanningline 5 to emit based on the received image data. Each red, green andblue pixel was appropriately arranged parallel in this manner, whereby afull-color display device was prepared.

It has been proved that a full-color moving image display deviceexhibiting a high luminance, a high durability and a highly visibilitycan be achieved by operating said full-color display.

Example 5 <Preparation of White Emitting Element and White Illumination>

A transparent electrode substrate of example 1 was subjected topatterning of an electrode having an area of 20 mm×20 mm, and α-NPD wasdeposited thereon at a layer thickness of 25 nm as a positive holeinjection/transport layer in a similar manner to example 1; and furtherthe aforesaid heating boat charged with H4, boat containing Examplecompound (159) and boat containing Ir-9 were supplied with an electriccurrent to deposit an emission layer having a layer thickness of 30 nm,while adjusting the evaporation rates of CBP as an emission host,Example compound (159) and Ir-9 as emission dopants to be 100:5:0.6.

Successively, BCP was deposited at 10 nm to provide a positive holeinhibition layer. Further, Alq₃ was deposited at 40 nm to provide anelectron transport layer.

Next, similar to example 1, a mask with square holes having a shapenearly same as a transparent electrode made of stainless steel wasarranged on an electron injection layer, and 0.5 nm of lithium fluorideas a cathode buffer layer and 150 nm of aluminum as a cathode weredeposited.

This element was equipped with a sealed can, which had a similarstructure and was prepared in a similar method to example 1, to prepareflat lamps shown in FIGS. 5 and 6.

Nearly white light was obtained when these lamps were supplied with anelectric current to prove that said lamp can be utilized as anillumination.

Example 6 <<Preparation of Organic EL Element 6-1>>: Present Invention

After carrying out patterning on a substrate (NA-45, produced by NHTechno Glass Co.) prepared in such a manner that ITO (being indium tinoxide) was applied at a thickness of 100 nm onto, a 100 mm×100 mm×1.1 mmglass substrate as an anode, the resulting transparent substrate fittedwith the above ITO transparent electrode was subjected to ultrasonicwashing employing isopropyl alcohol and dried via desiccated nitrogengas, and then subjected to UV ozone cleaning for 5 minutes.

A solution prepared by dilutingpoly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT/PSS,produced by Bayer Co., BASYTRON P A1 4083) with pure water to 70% byweight was applied to the resulting transparent substrate at 3,000 rpmover 30 seconds, employing a spin coating method, and subsequently driedat 200° C. over 1 hour, whereby a 30 nm thick positive hole injectiontransport layer was resulted.

A solution prepared by dissolving 30 mg of PO-1 of the present inventionin 3 ml of toluene was applied onto the resulting positive holeinjection transport layer at 1,000 rpm over 30 seconds, employing a spincoating method, and subsequently dried for one hour under vacuum,whereby a 80 mm thick emission layer was prepared.

The resulting layer was placed in a vacuum deposition apparatus, andsubsequently, the pressure of the vacuum tank was reduced to 4×10⁻⁴ Pa.Subsequently, 10 nm calcium as a cathode buffer layer was deposited,while 110 nm aluminum as a cathode was deposited, whereby Organic ELElement 6-1 was prepared.

<<Preparation of Organic EL Elements 6-2-6-17>>: Present Invention

Each of Organic EL Elements 6-2-6-17 was prepared in the same manner asOrganic Element 6-1, except that “PO-1” employed to prepare theluminance layer was replaced with each of PO-2, PO-3, PO-7, PO-8, PO-10,PO-11, PO-13, PO-15, PO-17, PO-20, PO-22, PO-23, PO-24, PO-25, PO-29,and PO-30.

<<Preparation of Organic EL Element 6-18>>: Comparative Example

Organic EL Element 6-18 was prepared in the same manner as Organic ELElement 6-1, except that 3 ml of the solution of PO-1 of the presentinvention was replaced with the solution described in following (A).

-   (A): Solution prepared by dissolving 30 mg of polyvinylcarbazole and    1.5 mg of Ir-13 (being a blue luminescent orthometalated complex)

<<Evaluation of Organic EL Elements 6-1-6-18>>

When resulting Organic EL Elements 6-1 through 6-18 were evaluated,after their preparation, the non-luminescent side of each Organic ELelement was covered with a glass case, and a 300 μm thick glasssubstrate was employed as a sealing substrate. Further, an epoxy basedradiation curing type adhesive (LAXTRUCK C0629B, produced by TOASynthetic Co.) was applied to the periphery as a sealing agent. Theresulting substrate was overlapped onto the above anode to come intoclose contact with the above transparent supporting substrate.Subsequently, UV radiation was exposed to the glass substrate side toresult in curing and sealing. Thus, the lighting device as shown inFIGS. 5 and 6 was formed and evaluation was carried out.

Subsequently, taking-out quantum efficiency and luminescent lifetimewere determined as follows.

<<Taking-Out Quantum Efficiency>>

Under a desiccated nitrogen gas atmosphere at 23° C., 2.5 mA/cm²constant-current was applied to each of Organic EL Elements prepared asabove and taking-out quantum efficiency (in %) was determined.Determination was carried out employing a spectral radiance meterCS-1000 (produced by Konica Minolta Holdings, Inc.).

<<Luminescent Lifetime>>

Under a desiccated nitrogen gas atmosphere at 23° C., 2.5 mA/cm²constant-current was applied to each of Organic EL Elements, and thetime, which was required for the change in which the luminance justafter luminance initiation (being initial luminance) was halved, wasdetermined. The determined value was designated the half lifetime(τ^(1/2)) and employed as an index for lifetime. Determination wascarried out also employing a spectral radiance meter CS-1000 (producedby Konica Minolta Holdings, Inc.).

Measurement results of the taking-out quantum efficiency and theluminescent lifetime of Organic EL Elements 6-1-6-18 were subjected torelative evaluation when each value of Organic EL Element 6-18 was to be100. Table 5 shows the results.

TABLE 5 Taking-out Organic Material Quantum EL in Yield Lumines-Lumines- Element emission (relative cent cent No. Layer value) LifetimeColor Remarks 6-1 PO-1 139 529 blue Inv. 6-2 PO-2 48 685 blue Inv. 6-3PO-3 152 531 blue Inv. 6-4 PO-7 160 458 blue Inv. 6-5 PO-8 141 624 blueInv. 6-6 PO-10 155 652 blue Inv. 6–7 PO-11 121 418 blue Inv. 6–8 PO-13172 713 blue Inv. 6–9 PO-15 154 851 blue Inv. 6–10 PO-17 132 366 blueInv. 6–11 PO-19 115 584 blue Inv. 6–12 PO-20 128 759 blue Inv. 6–13PO-22 168 611 blue Inv. 6–14 PO-24 188 763 blue Inv. 6–15 PO-25 176 826blue Inv. 6–16 PO-29 180 701 green Inv. 6–17 PO-30 168 274 red Inv. 6–18PVCz/Ir-13 100 100 blue Comp.

As can be seen from Table 5, by employing the polymer compound of thepresent invention in the emission layer, the taking-out quantumefficiency was significantly enhanced and electrical consumption wasmarkedly reduced, while the luminescent lifetime was also improved.

Further, Element (6-16) employing PO-29 of the present inventionresulted in green luminescence, while Element (6-17) employing PO-30 ofthe present invention resulted in red luminescence. Organic EL Elementsother than those resulted in blue luminescence.

1. An organic electroluminescent element material represented by Formula(1),

wherein Z is a heterocyclic ring comprising a substituent having asteric parameter value (Es) of −0.5 or less at the third atom of thering counted from a nitrogen atom attached to Z, the nitrogen atom beingcounted as the first atom; each X and Y is independently a carbon atomor a nitrogen atom; A is a group of atoms necessary to form a 5 or 6membered hydrocarbon ring or heterocyclic ring with X—C; B is—C(R₀₁)═C(R₀₂)—, —N═C(R₀₂)—, —C(R₀₁)═N—, or —N═N—, provided that eachR₀₁ and R₀₂ is independently a hydrogen atom or a substituent; X₁-L1-X₂is a bidentate ligand, provided that each X₁ and X₂ is independently acarbon atom, a nitrogen atom or an oxygen atom, and that L1 is a groupof atoms necessary to form the bidentate ligand with X₁ and X₂; m1 is aninteger of 1 to 3, and m2 is an integer of 0 to 2, provided that a sumof m1 and m2 is 2 or 3; and M₁ is a metal element selected from thegroup consisting of Groups 8 to 10 in the periodic table.
 2. An organicelectroluminescent element material represented by Formula (1B),

wherein each X and Y is independently a carbon atom or a nitrogen atom;A is a group of atoms necessary to form a 5 or 6 membered hydrocarbonring or heterocyclic ring with X—C; B is —C(R₀₁)═C(R₀₂)—, —N═C(R₀₂)—,—C(R₀₁)═N—, or —N═N—, provided that each R₀₁ and R₀₂ is independently ahydrogen atom or a substituent; X₁-L1-X₂ is a bidentate ligand, providedthat each X₁ and X₂ is independently a carbon atom, a nitrogen atom oran oxygen atom, and that L1 is a group of atoms necessary to form thebidentate ligand with X₁ and X₂; m1 is an integer of 1 to 3, and m2 isan integer of 0 to 2, provided that a sum of m1 and m2 is 2 or 3; and M₁is a metal element selected from the group consisting of Groups 8 to 10in the periodic table; and Zb is a group selected from the groupconsisting of:

provided that (*) indicates a position which binds to a nitrogen atom.3. The organic electroluminescent element material of claim 2, whereinZb in Formula (1B) has further a halogen atom.
 4. An organicelectroluminescent element material comprising a polymer having apartial structure represented by Formula (1B) of claim 2 in themolecule.
 5. An organic electroluminescent element material representedby Formula (2),

wherein R is a substituent having a steric parameter value (Es) of −0.5or less,; R₁ is a hydrogen atom or a substituent, and n1 is an integerof 1 to 4; R₂ is a hydrogen atom or a substituent, and n2 is an integerof 1 or 2; Z₁ is a group of atoms necessary to form a 5 or 6 memberedhydrocarbon ring or heterocyclic ring with C—C; Z₂ is a group of atomsnecessary to form a hydrocarbon ring or a heterocyclic ring with C—C;X₁-L1-X₂ is a bidentate ligand, provided that each X₁ and X₂ isindependently a carbon atom, a nitrogen atom or an oxygen atom, and thatL1 is a group of atoms necessary to form the bidentate ligand with X₁and X₂; m1 is an integer of 1 to 3, and m2 is an integer of 0 to 2,provided that a sum of m1 and m2 is 2 or 3; and M₁ is a metal elementselected from the group consisting of Groups 8 to 10 in the periodictable.
 6. The organic electroluminescent element material of claim 5,wherein in Formula (2), n1 is 2 or more and a plurality of R₁s forms aring by binding together.
 7. The organic electroluminescent elementmaterial of claim 5, wherein R₁ in Formula (2) is an aromatichydrocarbon having a substituent.
 8. The organic electroluminescentelement material of claim 5, wherein R₁ in Formula (2) is an aromaticheterocylic group or a non aromatic heterocylic group.
 9. The organicelectroluminescent element material of claim 5, wherein R₁ in Formula(2) is an alkoxy group or an aryloxy group.
 10. The organicelectroluminescent element material of claim 5, wherein R₂ in Formula(2) is a substituent.
 11. The organic electroluminescent elementmaterial of claim 5, wherein Formula (2) is further represented byFormula (3),

wherein R is a substituent having a steric parameter value (Es) of −0.5or less,; R₁ is a hydrogen atom or a substituent, and n1 is an integerof 1 to 4; each R₂ and R₃ is independently a hydrogen atom or asubstituent, n2 is an integer of 1 or 2 and n3 is an integer of 1 to 4;X₁-L1-X₂ is a bidentate ligand, provided that each X₁ and X₂ isindependently a carbon atom, a nitrogen atom or an oxygen atom, and thatL1 is a group of atoms necessary to form the bidentate ligand with X₁and X₂; m1 is an integer of 1 to 3, and m2 is an integer of 0 to 2,provided that a sum of m1 and m2 is 2 or 3; and M₁ is a metal elementselected from the group consisting of Groups 8 to 10 in the periodictable.
 12. The organic electroluminescent element material of claim 11,wherein Formula (3) is further represented by Formula (4),

wherein R is a substituent having a steric parameter value (Es) of −0.5or less,; R₁ is a hydrogen atom or a substituent, and n1 is an integerof 1 to 4; each R₂ and R₃ is independently a hydrogen atom or asubstituent, n2 is an integer of 1 or 2 and n3 is an integer of 1 to 3;X₁-L1-X₂ is a bidentate ligand, provided that each X₁ and X₂ isindependently a carbon atom, a nitrogen atom or an oxygen atom, and thatL1 is a group of atoms necessary to form the bidentate ligand with X₁and X₂; m1 is an integer of 1 to 3, and m2 is an integer of 0 to 2,provided that a sum of m1 and m2 is 2 or 3; and M₁ is a metal elementselected from the group consisting of Groups 8 to 10 in the periodictable.
 13. The organic electroluminescent element material of claim 12,wherein R₃ in Formula (4) is a hydrogen atom.
 14. The organicelectroluminescent element material of claim 5, wherein m2 in Formula(2) is
 0. 15. The organic electroluminescent element material of claim5, wherein R in Formula (2) is electron donative.
 16. The organicelectroluminescent element material of claim 5 exhibiting a firstemission wavelength of 400 to 500 nm.
 17. An organic electroluminescentelement comprising the organic electroluminescent element material ofclaim
 1. 18. An organic electroluminescent element comprising theorganic electroluminescent element material of claim
 2. 19. An organicelectroluminescent element comprising the organic electroluminescentelement material of claim
 5. 20. An organic electroluminescent elementcomprising an emission layer as a constituting layer of the element,wherein the emission layer comprises the organic electroluminescentelement material of claim
 5. 21. The organic electroluminescent elementof claim 20, wherein the emission layer further comprises: (i) acarboline derivative; or (ii) a condensed ring compound having astructure derived from carboline, wherein at least one of carbon atomsof a hydrocarbon ring in a carboline ring is substituted with a nitrogenatom.
 22. The organic electroluminescent element of claim 19, comprisinga positive hole inhibition layer as a constituting layer of the element,the positive hole layer containing: (i) a carboline derivative; or (ii)a condensed ring compound having a structure derived from carboline,wherein at least one of carbon atoms of a hydrocarbon ring in acarboline ring is substituted with a nitrogen atom.
 23. A display devicecomprising the organic electroluminescent element of claim
 17. 24. Adisplay device comprising the organic electroluminescent element ofclaim
 18. 25. A display device comprising the organic electroluminescentelement of claim
 19. 26. A lighting device comprising the organicelectroluminescent element of claim
 17. 27. A lighting device comprisingthe organic electroluminescent element of claim
 18. 28. A lightingdevice comprising the organic electroluminescent element of claim 19.